Theses authorised for defence

DOCTORAL DEGREE IN AEROSPACE SCIENCE AND TECHNOLOGY

• GASPARINO FERREIRA DA SILVA, LUCAS: High-performance low-dissipation algorithms for simulation of turbulent compressible flows
  
  Author: GASPARINO FERREIRA DA SILVA, LUCAS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN AEROSPACE SCIENCE AND TECHNOLOGY
  Department: Department of Physics (FIS)
  Mode: Normal
  Deposit date: 03/04/2024
  Reading date: 28/06/2024
  Reading time: 11:00
  Reading place: BSC Auditorium, Planta -1, Plaça Eusebi Güell 1-3, Barcelona
  Thesis director: LEHMKUHL BARBA, ORIOL | MIRA MARTÍNEZ, DANIEL
  Committee:
       PRESIDENT: RUBIO CALZADO, GONZALO
       SECRETARI: JOFRE CRUANYES, LLUÍS
       VOCAL: COLOMBO, ALESSANDRO
  Thesis abstract: Motivated by recent advances in computational technology aiming at exascale capabilities, which implies a need for applicationscapable of taking advantage of these new supercomputing architectures, this work will present two algorithms aimed at implementing an efficient and low-dissipation algorithm focused on LESand DNS of turbulent compressible flows.The basis for the algorithms is the Continuous Galerkin method applied to elements whose nodes and quadrature points areformed from the Gauss-Lobatto-Legendre roots, resulting in a SpectralElements Method. Throughout this work, it will be evidenced that this formulation leads to highly efficient kernels for discretizingthe convective and diffusive terms of the compressible Navier-Stokes equations, with the added benefit that the order of the scheme is coupled with the order of the shape functionpolynomials employed by the elements themselves, significantly simplifying the process of increasing the order of the scheme.To achieve a stable Total Variational Diminishing algorithm, the \acrshort{sem} scheme will be paired with an EntropyViscosity-based stabilization model and a suitable splitting of the nonlinear convective terms will be employed to eliminate aliasing issues that occur in the \acrshort{sem} formulation.This spatial discretization is then coupled with both an explicit and a semi-implicit scheme to account for the temporal nature ofthe flow equations. The explicit version of the algorithm is expected to be simple and efficient per time step, but due to its \acrshort{cfl} condition limitation, the semi-implicit version is alsoproposed to allow for better overall performance incases where the time-step becomes overly limited, such as in wall-bounded flows.Considering the focus on producing a \acrshort{cfd} application towards the exascale future, an important aspect of this work isthat both algorithms are proposed with a full \acrshort{gpu}implementation in mind: the use of accelerators is expected to be a key aspect of future supercomputing architectures, and thus itis important to design these algorithms with this in mind.Examples detailing the performance of both algorithms will be presented both in the case of a single device and when distributedarchitectures using multiple devices are employed.
  
• RADHAKRISHNAN, SARATH: NON-EQUILIBRIUM WALL MODELING IN LES OF HIGH-SPEED TRANSITIONAL FLOWS
  
  Author: RADHAKRISHNAN, SARATH
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN AEROSPACE SCIENCE AND TECHNOLOGY
  Department: Department of Physics (FIS)
  Mode: Normal
  Deposit date: 05/04/2024
  Reading date: 10/06/2024
  Reading time: 11:00
  Reading place: Sala de Actos Manuel Martí Recober (C/ Jordi Girona 1- 3, Edifici B6, Planta 0, Campus Nord, Barcelona)
  Thesis director: LEHMKUHL BARBA, ORIOL | MIRA MARTÍNEZ, DANIEL
  Committee:
       PRESIDENT: VINUESA MOLTIVA, RICARDO
       SECRETARI: RODRIGUEZ PEREZ, IVETTE MARIA
       VOCAL: ALCÁNTARA ÁVILA, FRANCISCO
  Thesis abstract: Wall-modeled large eddy simulation (WMLES) is a practical tool to perform the wall-bounded large eddy simulation (LES) with less computational cost by avoiding explicit resolution of the region near the wall. However, its use is limited in flows that have high non-equilibrium effects, like separation and/or transition. In this work, three wall modeling strategies are presented, two of them based on high-fidelity data. First, a technique is presented to improve the robustness of the state-of-the-art algebraic wall shear stress model. Second, an equilibrium-data-driven wall shear stress model is developed using the LES of the channel data. The key purpose of this is to estabilish the methodology of model development using high-fidelity data. The model is built using a machine learning technique that uses gradient-boosted regression trees (GBRT). The objective of the model is to learn the boundary layer of a turbulent channel flow so that it can be used in significantly different flows where the equilibrium assumptions are valid. The importance of selecting the appropriate data for training and the importance of choosing the input of the model are described. The model is validated a priori and a posteriori. A posteriori tests are conducted by implementing the model in a multiphysics solver and using it in the turbulent channel flow and in the flow over a wall-mounted hump. The performance of the model is compared with an algebraic wall shear stress model to understand the strengths and shortcomings of the data-based models and further improve the same. In the next step, the model is upgraded to a non-equilibrium wall model by using non-equilibrium data for the training. The high-fidelity data chosen for training include the Direct Numerical Simulation (DNS) of a double diffuser that has strong non-equilibrium flow regions and LES of a channel flow. The ultimate purpose of this model is to distinguish between equilibrium and non-equilibrium regions and to provide the appropriate wall shear stress. The ML system used for this study is also GBRT. The model is tested a priori and a posteriori. A posteriori tests are conducted on the diffuser, channel flows, flow over the hump, and junction flows. These tests showed that the model is very effective for corner flows and flows that involve relaminarization, while it performs rather less effectively in recirculation regions.
  

DOCTORAL DEGREE IN ARCHITECTURAL, BUILDING CONSTRUCTION AND URBANISM TECHNOLOGY

• BENINCA, LETIANE: Multi-objective optimization for social multifamily housing: Minimizing heating and cooling demand
  
  Author: BENINCA, LETIANE
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ARCHITECTURAL, BUILDING CONSTRUCTION AND URBANISM TECHNOLOGY
  Department: Department of Architectural Technology (TA)
  Mode: Change of supervisor
  Deposit date: 11/04/2024
  Reading date: 10/05/2024
  Reading time: 13:00
  Reading place: Presencial Sala de Graus ETSAB. Planta Baixa + videoconferència:meet.google.com/cpp-awed-vth
  Thesis director: CRESPO SÁNCHEZ, EVA | PASSUELLO, ANA CAROLINA
  Committee:
       PRESIDENT: DE MOURA FERREIRA DANILEVICZ, ANGELA
       SECRETARI: KAMPOUROPOULOS, KONSTANTINOS
       VOCAL: CÓSTOLA, DANIEL
  Thesis abstract: The field of architecture and engineering is currently experiencing significant changes due to advances in technology and the growing role of Artificial Intelligence. This shift is largely driven by the growing urgency of promoting more efficient buildings, especially considering its substantial impact on global greenhouse gas emissions and energy usage. Consequently, it is becoming important to focus on practical design choices and utilize effective strategies to enhance energy efficiency and overall building performance. This thesis presents a comprehensive approach to optimize the shape, solar orientation, and envelope configuration of social residential buildings in a humid subtropical climate (Koppen classification: Cfa) in the southern region of Brazil. The main objective is to simultaneously minimize both heating and cooling demands, and present optimal performance design and parameter ranges to improve efficiency energy in multifamily buildings. To achieve this, the study utilizes multi-objective optimization techniques with the support of a non-dominated sorting genetic algorithm (NSGA-II). The simulations are conducted using the EnergyPlus while the optimization process is implemented through Python programming. This extensive computational effort involves a total of 480,000 simulations. The results of the optimization process demonstrate that by carefully selecting the optimal solar orientation, significant reductions in energy demand can be achieved. For instance, optimizing the solar orientation alone can lead to energy demand reductions of up to 5% for linear buildings and 11% for H buildings, when linked to the surroundings. Furthermore, when the envelope is properly addressed the energy demand between shapes achieves almost the same value. Moreover, the optimization of the building envelope configuration further enhances energy efficiency, resulting in remarkable reductions in total energy demand. In particular, linear buildings can achieve up to 60% reduction in energy demand, while H buildings reach up to 63% reduction. These findings highlight the potential benefits of considering solar orientation, surrounding shadows, and envelope design simultaneously during the early design stages of a project. The proposed three-phase optimization framework evaluates different parameter alternatives and presents a pratical guidelines to make informed decisions about the most energy-efficient configurations.
  

DOCTORAL DEGREE IN AUTOMATIC CONTROL, ROBOTICS AND VISION

• ORTI NAVARRO, JOAN: The Surface Defect Identification Problem in The Industry: A Novel Approach with Semantic Segmentation and Generative Adversarial Networks
  
  Author: ORTI NAVARRO, JOAN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN AUTOMATIC CONTROL, ROBOTICS AND VISION
  Department: Department of Automatic Control (ESAII)
  Mode: Normal
  Deposit date: 18/03/2024
  Reading date: 10/05/2024
  Reading time: 11:00
  Reading place: Sala Actes de la Facultat de Matemàtiques i Estadística (FME), Campus Diagonal Sud, Carrer de Pau Gargallo, 14, 08028 Barcelona
  Thesis director: MORENO NOGUER, FRANCESC D'ASSIS | PUIG CAYUELA, VICENÇ
  Committee:
       PRESIDENT: SERRATOSA CASANELLES, FRANCESC ASSIS
       SECRETARI: GRAU SALDES, ANTONI
       VOCAL: VENTURA ROYO, CARLES
  Thesis abstract: Surface inspection of coated surfaces in the automotive industry, traditionally has been a manual process in charge of keen eye operators in charge of inspecting the whole car body. However, as might be deducted, manual inspections often lack repetitiveness and reliability, very much desired in a such a strict sector. Computer vision tackled this problem with the first automated defect detection systems, pinpointing the defects in the car body and their size. Nevertheless, as these systems are constrained to just detection, the operator is still in charge of properly labelling the defects to rework them correctly. Additionally, there is a lack of traceability between the process and the defects themselves, taking longer to identify the root causes of faulty paint shop facilities.In this thesis, we address the multidisciplinary problem of defect identification in specular surfaces, with two main research lines. In the first one, we developed a novel illumination approach based on indirect diffuse lighting, in contrast with the conventional specular reflection. Together with a high resolution camera, we demonstrated an important improvement in terms of defect recognition with respect to the existing defect detection systems. These results are assessed with specialized auditors from the SEAT Martorell factory.The second research line, oriented to computer vision, explore the possibilities of implementing a deep learning solution for industrial defect identification. We developed a fast and reliable context aggregation model, featuring dilated convolutions and residual connections between opposite layers. This model is then trained following a loss leverage between classification and segmentation, for a smoother training procedure. Additionally, in order to cope the frequent class imbalances in the industrial datasets, we developed a guided-crop image augmentation strategy, based on cropping real defect randomly into non-defective images to generate synthetic new samples. The results state that the combination of this model with this augmentation strategy is able to outperform well-known segmentation models.Eventually, for data scarcity situations, we resorted to image synthesis methods to generate new fake samples. Models like Pix2pix have proven to be able to generate close to real im- ages, helping the segmentation model to converge faster than with the previous guided-crop image augmentation technique. Later, this generative method will be surpassed by a more sophisticated one, which features spatially-adaptive normalization layers that help to synthe- size images even without an encoder. Overall, it demonstrated good capabilities in multiple industrial datasets.
  

DOCTORAL DEGREE IN BIOINFORMATICS

• CABRERA PASADAS, MÓNICA: Exploring the impact of p53 activation on spatio-temporal genome topology
  
  Author: CABRERA PASADAS, MÓNICA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN BIOINFORMATICS
  Department: Department of Statistics and Operations Research (EIO)
  Mode: Normal
  Deposit date: 27/10/2023
  Reading date: 09/07/2024
  Reading time: 10:00
  Reading place: Sala d'Actes de l'FME, Edifici U, Campus Sud
  Thesis director: JAVIERRE MARTINEZ, BIOLA M | VALENCIA HERRERA, ALFONSO
  Committee:
       PRESIDENT: MARTI-RENOM, MARC A
       SECRETARI: DELICADO USEROS, PEDRO FRANCISCO
       VOCAL: RAMOS RODRIGUEZ, MIREIA
       VOCAL NO PRESENCIAL: STIK, GREGOIRE
       VOCAL NO PRESENCIAL: GÓMEZ MELIS, GUADALUPE
  Thesis abstract: The year I started this Ph.D. (2019) was the 40th anniversary of the discovery of p53 and the 30th anniversary of its characterization as a tumor suppressor. Approximately, half of all human cancers carry mutations or deletions of the p53 gene, while the other half have disruptions to the p53 signaling pathway. Nevertheless, despite decades of extensive research the precise molecular mechanisms underpinning p53-mediated gene regulation and its tumor-suppressive efficacy remain partially elucidated.Under non genotoxic or oncogenic stressed conditions, the MDM2 protein promotes ubiquitination and proteasome-mediated degradation of p53 maintaining low cellular levels. However, upon encountering cellular stress, the p53-MDM2 interaction is disrupted leading to p53 accumulation and activation. Once active, p53 promotes critical cell fate decisions such as cell cycle arrest, apoptosis, or senescence by transactivating an array of target genes, leading to effective tumor regression. Consequently, the loss of p53 functionality is intrinsically linked to cancer susceptibility, rendering p53 an enticing candidate for anti-cancer therapeutic interventions. Cis-regulatory elements master gene expression through the control of transcription in temporal and spatial dimensions. However, the mechanisms by which p53 engages the genome in the context of 3D chromatin to activate transcription are not well understood ¿the interplay between p53 and 3D genome organization has remained unexplored to date.This doctoral thesis investigates p53s ability to reconfigure the genome and govern transcriptional regulation by inducing alterations in the temporal and spatial genome structure. It is the hypothesis of this dissertation that p53 exerts its influence by modulating physical connections between regulatory elements, enhancers, and gene promoters via the manipulation of DNA loops.To rigorously assess this proposition, a comprehensive investigation into the potential ramifications of p53 activation in HCT116 cell lines achieved through pharmacologically inhibiting MDM2 with Nutlin-3a drug has been outlined. This approach synergistically integrates diverse genomic datasets, encompassing Hi-C, Promoter Capture Hi-C, RNA-seq, and ChIP-seq methodologies. The analysis unveils that p53 activation precipitates both direct and indirect modifications in genome architecture, manifesting within minutes of its induction. By deciphering the nexus between 3D genome organization and p53-driven transcriptional regulation, this thesis aspires to help in the unravel avenues for therapeutic intervention in the realm of cancer treatment.
  

DOCTORAL DEGREE IN BIOMEDICAL ENGINEERING

• SAYOLS BAIXERAS, NARCÍS: Cognitive Robot Control Strategies for Complex Surgical Environments
  
  Author: SAYOLS BAIXERAS, NARCÍS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN BIOMEDICAL ENGINEERING
  Department: Department of Automatic Control (ESAII)
  Mode: Normal
  Deposit date: 11/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: CASALS GELPI, ALICIA | HERNANSANZ PRATS, ALBERTO
  Committee:
       PRESIDENT: DALL\'ALBA, DIEGO
       SECRETARI: FRIGOLA BOURLON, MANEL
       VOCAL: AVILÉS RIVERO, ANGÉLICA
  Thesis abstract: This thesis aims to contribute to the development of robotics autonomy in complex tasks based on the cognitive control paradigm. Cognition is a multidisciplinary approach aimed to provide robotic systems with intelligent and autonomous behaviour that should learn and reason about how to respond in front of complex tasks and environments.Cognition involves aspects as perception, awareness, interpretation of human actions, learning, planning, anticipating and dynamic response to changes in the working conditions and in the interaction with humans. Autonomy is intended to partially substitute and/or complement the human faculties at the level of perception, analysis and execution. Increasing the level of autonomy of robots allows focusing the humans cognitive load on high level decisions and actions, in aspects where the human factor is essential: contextualisation of information, specific expertise, medical knowledge and complex decision-making among others. Furthermore, robots improve the properties of humans in certain aspects such as precision, repeatability, absence of fatigue or response efficiency in terms of time and accuracy.This thesis addresses different key aspects of robotic autonomy: perception, planning and dynamic execution of actions and, finally, the control structures required for efficient control and their integration in robotic systems.This thesis combines a global theoretical approach supported by practical applications based on the field of robot-assisted minimally invasive surgery. This field has been chosen for two main reasons: the social impact involved in the improvement of surgery and, secondly, because this field of application is highly demanding from both, human and robotic perspective.The experimental phases have focused on various surgical robotic. First, a teleoperated platform with a single robot has been used aimed at minimally invasive fetal surgery in which a cognitive system offers a certain level of autonomy to generate trajectories in collision-free spaces, increasing patient safety and decreasing the cognitive load of surgeons in navigation and interaction tasks within the intra-uterine region. Second, a multi-robot architecture to execute auxiliary actions in a human-robot cooperative system: the main surgeon performs the surgical actions while the auxiliary robots perform, autonomously, auxiliary surgical tasks. With this configuration the experimentation focuses on minimally invasive radical prostatectomy surgery.Thus, the thesis addresses the perception of the anatomical environment, considering the limitations of data acquisition in terms of quality and quantity, as well as the absence of anatomical markers. The next topic that the thesis addresses is the dynamic planning of actions. Different application paradigms have been studied, such as direct human-robot interaction using haptic guidance, movement planning in pseudo-structured environments and, active planning and control in dynamic environments. These proposed environments respond to different surgical scenarios within minimally invasive techniques.Finally, cognitive control applied to robotic platforms is addressed. The followed approach is based on the multi-level decomposition of complex tasks (e.g. surgical procedure) defining all potential states and transitions. This decomposition translates into the use of deterministic and robust control structures that restrict falling into uncontrollable or unexpected situations that put at risk, in the application case, the patient, the surgeons or the auxiliary personnel.Control structures also consider human-robot interaction, robots coordination and cooperation, interaction with the work environment and restrictions imposed by surgery and patient safety.The integration of all these modules: perception, planning and cognitive control, demonstrates the advances achieved in cognitive robotics and their applicability towards a more autonomous robotic surgery.
  

DOCTORAL DEGREE IN BUSINESS ADMINISTRATION AND MANAGEMENT

• HINOJOSA I RECASENS, JOSEP DOMINGO: Investigación sobre la persistencia, el cambio y la materialidad de la identidad organizacional: entrevistas a expertos y el caso de una empresa centenaria
  
  Author: HINOJOSA I RECASENS, JOSEP DOMINGO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN BUSINESS ADMINISTRATION AND MANAGEMENT
  Department: Department of Management (OE)
  Mode: Normal
  Deposit date: 05/03/2024
  Reading date: 30/05/2024
  Reading time: 11:30
  Reading place: Lectura públicaa l' Aula 28.8 de l'Escola Tècnica Superior d'Enginyeria Industrial de Barcelona (ETSEIB)- UPC
  Thesis director: SUNYER TORRENTS, ALBERT
  Committee:
       PRESIDENT: GARCÍA ÁLVAREZ, MARIA ERCILIA
       SECRETARI: PONS PEREGORT, OLGA
       VOCAL: SELVA OLID, CLARA
  Thesis abstract: ContextThis thesis investigates organizational identity, its persistence and change, and the relationship between identity and material objects. Organizational identity is what the members of an organization answer when they ask themselves: Who are we? and what do we do as an organization?. As a field of research, organizational identity has been gaining relevance in recent decades, especially since the authors Albert and Whetten (1985) established the academic foundations to characterize this concept through the attributes that identity must have: centrality, endurance and differentiation. This characterization was generally accepted by the scientific community and was not questioned for years; it is still considered relevant today. Organizational identity is a broad and complex topic that has been explored by various researchers using qualitative methods. Identity can evolve as organizational practices and narratives are reinterpreted. Some authors consider that identity is dynamic and that it can change as the organization evolves. In this thesis we develop an exploratory research on organizational identity, paying special attention to how identity can adapt, change and be instantiated by material objects. Specifically, this thesis has been structured based on two lines of research: The first line of research studies the persistence of organizational identity and its changes over time, the second line explores the possible relationships between the organizational identity and material artifacts.JustificationThere remains an interesting path to follow in research on organizational identity. Currently, organizational identity is part of the strategic debates and communication plans of many organizations, highlighting the relevance of this concept that can be considered the DNA of an organization. The purpose of this research is to deepen the understanding of organizational identity by exploring how it evolves when the environment changes, when new strategies or different events occur in which identity may face internal or external tensions. Finally, a single in-depth case study is developed exploring the relationships between the identity of an organization and some of its material artifacts.ContributionsThis study has shown that physical objects are part of an identity system that, including other intangible elements, such as verbal communication and narratives, support, instantiate and communicate organizational identity over time. This research results extend the literature on identity, and on the influence and use of material identity objects. The in-depth case study has shown that physical objects has been used to support, instantiate and communicate organizational identity. The data induction process has characterized three different categories of physical objects that provide identity meanings: primal artifacts, identity markers and artifacts created ad hoc.LimitationsThis work provides an exciting opportunity for future research to extend these findings by examining the persistence, change, and materiality of identity in other organizational contexts and industries.
  

DOCTORAL DEGREE IN CHEMICAL PROCESS ENGINEERING

• AGUILAR MORENO, MIGUEL: Liquid-Liquid membrane contactors for sustainable ammonia recovery and valorization: experimental insights, novel approaches and applications
  
  Author: AGUILAR MORENO, MIGUEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CHEMICAL PROCESS ENGINEERING
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 16/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: CORTINA PALLAS, JOSE LUIS | VALDERRAMA ANGEL, CESAR ALBERTO
  Committee:
       PRESIDENT: DOSTA PARRAS, JOAN
       SECRETARI: GIBERT AGULLO, ORIOL
       VOCAL: REZAKAZEMI, MASHALLAH
  Thesis abstract: This comprehensive research represents a significant stride in the exploration of innovative strategies aimed at enhancing ammonia recovery within diverse wastewater streams. The study is structured into distinct phases, each addressing crucial aspects of the ammonia recovery process. In the initial phase, the research focuses on augmenting membrane contactor performance, employing coagulation-flocculation (C/F) and aeration as preliminary treatments. The outcomes of this phase demonstrate substantial increases in both the mass transfer coefficient and overall efficiency ofammonia recovery, particularly notable when treating the real sidestream centrate. A pivotal finding underscores the efficacy of dosing aluminum sulphate (Al2(SO4)3) at 30 mg Al+/L in the C/F process, yielding remarkable efficiencies in the removal of chemical oxygen demand (COD), turbidity, and total suspended solids (TSS). Into the second phase, the study delves into the sustainable application of liquid-liquid membrane contactors (LLMC) for ammonia recovery. An array of experimental conditions is meticulously explored, with the results illuminating the considerable impact of replacing the acid washing liquid between steps on the overall performance of the LLMC. Additionally, the study highlights the nuanced relationship between the initial ammonia concentration and the subsequent recovery, providing valuable insights. This phase effectively showcases the potential versatility and efficiency of LLMCs in the valorization of ammonia within wastewater streams. The third and final phase introduces a novel asymmetric hollow fiber liquid-liquid membrane contactor (HF-LLMC) with distinctive selectivity for ammonia over water. The investigation entails a comprehensive examination of various operational parameters, including feed and acid flow rates, mass transfer coefficients, and acid consumption. Notably, the results affirm the high selectivity of the HF-LLMC for ammonia, coupled with minimal water transfer. This establishes the HF-LLMC as a promising technology for the recovery and concentration of ammonium in diluted urban and industrial streams. The amalgamation of these findings, approached with a global perspective, significantly contributes not only to the advancement of sustainable nutrient recovery technologies but also underscores their pragmatic feasibility for implementation within the frameworks of the circular economy and efficient resource management.
  
• MESA GÓMEZ, ADRIANA MARÍA: Analysis and modelling of natech accidents originated by strong winds
  
  Author: MESA GÓMEZ, ADRIANA MARÍA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CHEMICAL PROCESS ENGINEERING
  Department: Department of Chemical Engineering (EQ)
  Mode: Change of supervisor
  Deposit date: 11/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: CASAL FABREGA, JOAQUIM | MUÑOZ GIRALDO, FELIPE | SANCHEZ SILVA, EDGAR MAURICIO
  Committee:
       PRESIDENT: PLANAS CUCHI, EULALIA
       SECRETARI: PALACIOS ROSAS, ADRIANA
       VOCAL: DEMICHELA, MICAELA
  Thesis abstract: In recent decades, there has been an increase in the frequency of natural events, coinciding with the simultaneous development of industrial activities in many countries. Consequently, the frequency of Natech accidents, which are technological disasters triggered by natural hazards, has also risen. This trend has spurred researchers to explore new risk analysis methods to prevent and mitigate potential damage to populations, the environment, and industrial facilities. There is a growing awareness in the literature about the impact of natural events, particularly when they occur concurrently, cascade, or accumulate over time.This thesis proposes a research initiative to conduct a risk assessment that includes the Natech risk associated with strong winds. The primary objective is to develop a methodology for analyzing Natech risk in storage units in coastal zones that are particularly vulnerable to extreme weather events.Firstly, the thesis introduces the integration of natural events, specifically strong winds, into a quantitative Natech risk analysis methodology. This integration represents a significant advancement in assessing the potential impacts of technological accidents triggered by natural events. By incorporating strong winds as a hazard, the methodology offers a more comprehensive approach to evaluating the vulnerability of industrial facilities, especially storage tanks, to natural-technological events. This integration enables stakeholders to better understand and quantify the risks posed by Natech events involving strong winds, facilitating the implementation of targeted mitigation measures and enhancing preparedness. Ultimately, it contributes to improving the resilience of industrial facilities and surrounding communities to the risks posed by natural events.Secondly, the thesis describes the development of two models for environmental and socioeconomic risk assessment, respectively. These models provide a comprehensive framework for evaluating the potential environmental and socioeconomic impacts of Natech events, thereby enhancing the understanding of the overall risk landscape. By incorporating previously overlooked vulnerable elements, such as cultural heritage sites, sensitive environmental areas, water catchment sites, and so on, the models offer a more holistic perspective on Natech risks, ensuring that mitigation strategies can protect not only human safety and infrastructure, but also socioeconomic and environmental assets.Thirdly, the thesis outlines the development of a computational tool designed to facilitate the implementation of these models. This tool streamlines the risk assessment process, enabling stakeholders to analyze and manage Natech risks efficiently.Overall, the generation of these models and the accompanying computational tool represents a significant advancement in Natech risk management. By integrating environmental and socioeconomic considerations into the risk assessment process, these models provide a more robust foundation for decision-making and emergency preparedness, ultimately contributing to the resilience of communities and ecosystems in the face of Natech events. Finally, the methodology is applied in a case study to verify its applicability
  
• NASR ESFAHANI, KOUROSH: Mathematical modeling of advanced oxidation processes for the efficient wastewater treatment: Integrated Management of advanced oxidation processes and conventional Bio-Processes for the removal of recalcitrant components
  
  Author: NASR ESFAHANI, KOUROSH
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CHEMICAL PROCESS ENGINEERING
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 28/03/2024
  Reading date: 02/07/2024
  Reading time: 11:00
  Reading place: Sala Polivalent de l'Edifici I, Planta baixa, Campus Diagonal-Besòs
  Thesis director: PEREZ MOYA, MONTSERRAT | GRAELLS SOBRE, MOISES
  Committee:
       PRESIDENT: PAIS VILAR, VÍTOR JORGE
       SECRETARI: SOLER TURU, LLUIS
       VOCAL: GARCIA MONTAÑO, JULIA
  Thesis abstract: The objective of this thesis is to contribute to the development of mathematical modeling of Advanced Oxidation Processes (AOPs) aimed at the competent treatment of recalcitrant organic compounds in wastewater. In particular, the Ph.D. thesis first focuses on developing mathematical models of AOPs, implementing these models in software tools, and enabling a deeper understanding of the complex nature of these processes through the detailed simulation of the evolution of chemical species along the reaction time for diverse and unexplored scenarios. Hence, these tools are next used for fitting the models to the experimental data obtained in the laboratory in the course of the thesis or reported in the literature. The fitted models are analyzed and refined through sensitivity analysis techniques, and finally, they are validated and their accuracy assessed. Models are mainly used for addressing operational issues, but also design aspects are considered in regard of the simulation of integrated processes using AOPs and conventional biotreatment processes.The thesis specifically addresses the development of a model for AOPs, above all photo-Fenton processes, including flexible H2O2 supply given as a function of time. The model contributes a practical tool aimed at providing model-based simulation for solving the problem of the management of the H2O2 dosage profile of the photo-Fenton process.The thesis also addresses the problem of the pH dependency of the photo-Fenton by modeling the possibility of performing the photo-Fenton process at near-neutral pH. This is studied by considering the use of iron complexing agents such as ethylenediamine disuccinic acid (EDDS). In a subsequent stage, as a step forward in improving photo-Fenton processes, a reported kinetic model of the Fe(3+)-EDDS mediated photo-Fenton process is extended to include the reactions occurring in the absence of H2O2, when EDDS(¿ 3- )radical generated from the lysis of the Fe(3+)-EDDS complex is responsible for the organic matter degradation. This is achieved by adopting a novel semi-empirical approach based on lumping radical species.Ozonation of wastewater is also studied as a different case of AOPs, focusing in the modeling of ozone decay during the treatment of secondary effluents containing organic matter. This is addressed by proposing a new model, based again in the used of lumped or surrogate concentrations. The ozone model developed is shown to be capable of describing the complex profile of the ozone at different initial concentrations, and has proved accurate to describe the experimental data obtained in the lab, as well as data reported in the literature.The modeling approach adopted in this thesis has also been used to explore integrated processes combining AOPs with other processes, namely conventional biotreatment processes which main acknowledged limitation is the incapacity to remove recalcitrant compounds from wastewaters. The study combined the AOP models developed with standard models such as ASM1 to map the correspondence between the variables employed in each model, and produce the simulation of different scenarios combining these two technologies.As a final remark, the thesis has also addressed the design and development of chemical reactors, particularly prototypes for photo-Fenton processes using 3D-printing. This last study addresses the selection of materials according to different criteria for reactor prototyping and subsequent testing of the chemical suitability of the reactor for carrying out AOPs.
  

DOCTORAL DEGREE IN CIVIL ENGINEERING

• GÓMEZ DUEÑAS, SANTIAGO: Unraveling Hydrological Dynamics: Climate and Human Implications in the Magdalena River Streamflow and its Interaction with Ciénaga Grande de Santa Marta Wetland
  
  Author: GÓMEZ DUEÑAS, SANTIAGO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CIVIL ENGINEERING
  Department: (DECA)
  Mode: Normal
  Deposit date: 16/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: BATEMAN PINZON, ALLEN
  Committee:
       PRESIDENT: SOLÉ, AURELIA
       SECRETARI: DE MEDINA IGLESIAS, VICENTE CÉSAR
       VOCAL: LA ROCCA, MICHELE
  Thesis abstract: This study offers a comprehensive understanding of the hydrological dynamics of the Magdalena River (MR) basin, located in Colombia. Multiple elements that affect streamflow were analyzed, such as climate-forcing drivers and human-induced ones, to understand the complex interactions that shape the region's hydrology.Firstly, the influence of many factors on the flow of water downstream of the Magdalena River was studied. The research identified El Niño southern oscillation (ENSO) episodes as crucial climate-forcing drivers and human-induced modifications such as reservoir evaporation. The complex nature of streamflow changes over time was highlighted by showing the variations in the average, volume, and maximum streamflow, as well as oscillations in evaporation and minimum streamflow, especially during positive ENSO episodes. These findings offer important insights into the changing hydrological regime of the MR basin, emphasizing the complex combination of elements that influence its flow patterns throughout time.Moreover, the study explored the hydrological connection between the MR and the Ciénaga Grande de Santa Marta (CGSM) wetland, revealing the interdependence of these two ecosystems. For this, the study explores the vulnerability of downstream habitats, especially wetlands, to changes in streamflow inputs by taking a broad approach that views the entire wetland as a unified unit. It identified crucial threshold ranges where the inflow from the Magdalena River to the CGSM becomes uncertain. This analysis highlights the urgent need to understand the interactions between water flow and wetland ecosystems and their significant impact. Furthermore, the present research utilizes Long Short-Term Memory (LSTM) neural network models to predict streamflow changes at the Calamar gauging station. The goal was to improve the precision of streamflow predictions by combining data from several gauging stations and reservoir evaporation records. Finally, this study can help enhance the comprehension of the intricate hydrological processes in the MR basin, revealing the interconnected effects of climate fluctuations, human actions, and ecosystem dynamics. In this context, this research sets the foundation for creating well-informed water resource management strategies in Colombia that protect wetland ecosystems' ecological health and adaptability in the face of ongoing environmental changes.
  

DOCTORAL DEGREE IN COMPUTER ARCHITECTURE

• FERRIOL GALMÉS, MIQUEL: Network modeling using graph neural networks
  
  Author: FERRIOL GALMÉS, MIQUEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTER ARCHITECTURE
  Department: (DAC)
  Mode: Normal
  Deposit date: 10/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: CABELLOS APARICIO, ALBERTO | BARLET ROS, PERE
  Committee:
       PRESIDENT: PESCAPÈ, ANTONIO
       SECRETARI: ARIAS VICENTE, MARTA
       VOCAL: RÉTVÁRI, GÁBOR
  Thesis abstract: Network modeling is central to the field of computer networks. Models are useful in researching new protocols and mechanisms, allowing administrators to estimate their performance before their actual deployment in production networks. Network models also help to find optimal network configurations, without the need to test them in production networks. Arguably, the most prevalent way to build these network models is through the use of discrete event simulation (DES) methodologies which provide excellent accuracy. State-of-the-art network simulators include a wide range of network, transport, and routing protocols, and are able to simulate realistic scenarios. However, this comes at a very high computational cost that depends linearly on the number of packets being simulated. As a result, they are impractical in scenarios with realistic traffic volumes or large topologies. In addition, and because they are computationally expensive, they do not work well in real-time scenarios.Another network modeling alternative is Queuing Theory (QT) where networks are represented as inter-connected queues that are evaluated analytically. While QT solves the main limitation of DES, it imposes strong assumptions on the packet arrival process, which typically do not hold in real networks.In this context, Machine Learning (ML) has recently emerged as a practical solution to achieve data-driven models that can learn complex traffic models while being extremely accurate and fast. More specifically, Graph Neural Networks (GNNs) have emerged as an excellent tool for modeling graph-structured data showing outstanding accuracy when applied to computer networks. However, some challenges still persist:1. Queues and Scheduling Policies: Modeling queues, scheduling policies, and Quality-of-Service (QoS) mappings within GNN architectures poses another challenge, as these elements are fundamental to network behavior.2. Traffic Models: Accurately modeling realistic traffic patterns, which exhibit strong autocorrelation and heavy tails, remains a challenge for GNN-based solutions.3. Training and Generalization: ML models, including GNNs, require representative training data that covers diverse network operational scenarios. Creating such datasets from real production networks is unfeasible, necessitating controlled testbeds. The challenge lies in designing GNNs capable of accurate estimation in unseen networks, encompassing different topologies, traffic, and configurations.4. Generalization to Larger Networks: Real-world networks are often significantly larger than testbeds. Scaling GNNs to handle networks with hundreds or thousands of nodes is a pressing challenge, one that requires leveraging domain-specific network knowledge and novel architectural approaches.This dissertation represents a step forward in harnessing Graph Neural Networks (GNN models) for network modeling, by proposing a new GNN-based architecture with a focus on addressing these critical challenges while being fast and accurate.
  
• GÓMEZ SÁNCHEZ, GONZALO: Exploring genomic datasets through machine learning methods leveraging high-performance computing
  
  Author: GÓMEZ SÁNCHEZ, GONZALO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTER ARCHITECTURE
  Department: (DAC)
  Mode: Normal
  Deposit date: 16/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: BERRAL GARCÍA, JOSEP LLUÍS | CARRERA PÉREZ, DAVID
  Committee:
       PRESIDENT: GARCÍA LÓPEZ, PEDRO
       SECRETARI: RUIZ RAMÍREZ, MARC
       VOCAL: CIRILLO, DAVIDE
  Thesis abstract: In recent years, the exponential increase of generated data has raised the need for implementing new methodologies to process the huge datasets being created. High-Performance Computing (HPC) brings together a set of technologies mainly based on parallel computing that help reduce the time expended analyzing these datasets. A research field where these technologies are needed is Computational Genomics. Furthermore, the complexity of the genomic datasets limits the use of basic conventional methods for the discovery of complex significant relations, introducing the need for Machine learning (ML) algorithms and robust statistical methods to better classify these variants. In the first part of the thesis, we aim to identify complex patterns of somatic genomic rearrangements in cancer samples, which are triggered by internal cellular processes and environmental factors. The problem of classification becomes particularly challenging when considering thousands of rearrangements at a time, often composed of multiple DNA breaks, increasing the difficulty in classifying and interpreting them functionally. Here we present a new statistical approach to analyze structural variants (SVs) from 2,392 tumor samples from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium and identify significant recurrence. The proposed methodology is able not only to identify complex patterns of SVs across different cancer types but also to prove them as not random occurrences, identifying a new class of pattern composed of three SVs that was not previously described. In the second part of the thesis, we approach another challenge of human genetics, which is the study of the relation between single nucleotide variants (SNVs) and complex diseases, such as Type 2 Diabetes, Asthma, or Alzheimer's. The study of these disease-variant associations is usually performed in a single independent manner, disregarding the possible effect derived from the interaction between genomic variants. Here, we have created a containerized framework that uses Multifactor Dimensionality Reduction (MDR) to detect combinations of variants associated with Type 2 Diabetes (T2D), called Variant Interaction Analysis (VIA). This methodology has been tested in the Northwestern University NUgene project cohort using a subset of 1,883,192 variant pairs with some degree of association with T2D and identifying a subset of 104 significant pairs, two exhibiting a potential functional relationship with T2D. The developed algorithm has been released in an open-source repository, including the containerized HPC framework, which can be used to search for significant pairwise interactions in other datasets.In both frameworks developed within the thesis, the use of large-scale supercomputing architectures has been a hard requirement to find relevant clinical indicators. To ensure open and broad access to HPC technologies, governments, and academia are pushing toward the introduction of novel computing architectures in large-scale scientific environments. This is the case of RISC-V, an emerging open standard instruction-set architecture. To evaluate such technologies, in the last two parts of the thesis, we propose the use of our VIA use case as a benchmarking, providing the first genomic application for RISC-V. With this use case, we provide a representative case for heavy ETL (Extract, Transform, Load) data processing. We developed a version of the VIA workload for RISC-V and adapted our implementation in x86-based supercomputers (e.g. Marenostrum IV at the Barcelona Supercomputing Center (BSC)) to make a fair comparison with RISC-V, since some technologies are not available there. With this benchmark, we have been able to indicate the challenges and opportunities for the next RISC-V developments and designs to come, from a first comparison between x86 and RISC-V architectures on genomic workload executions over real hardware implementations.
  

DOCTORAL DEGREE IN COMPUTING

• ALONSO ALONSO, JESUS: Dynamic Terrain Modeling
  
  Author: ALONSO ALONSO, JESUS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTING
  Department: Department of Computer Science (CS)
  Mode: Normal
  Deposit date: 18/03/2024
  Reading date: 08/05/2024
  Reading time: 12:00
  Reading place: Aula Capella de l'ETSEIB, campus sud, Avd.Diagonal 647
  Thesis director: JOAN ARINYO, ROBERT
  Committee:
       PRESIDENT: CHOVER, MIGUEL
       SECRETARI: ARGUDO MEDRANO, OSCAR
       VOCAL: BOSCH GELI, CARLES
  Thesis abstract: This work explores terrain modelling techniques that provide a comprehensive experience in terms of graphical representation, physics interaction and dynamic updates in real-time. In particular, our focus revolves around the creation of a system able to: 1) capture any possible feature we find on terrains, 2) maintain an accurate level of detail, 3) offer rendering and navigation in real-time, 4) include the option of performing dynamic updates in real-time, and 5) support physical interactions of entities also in real-time.Once previous models from the literature are reviewed, two models are proposed that take a digital elevation model as the base structure. The former follows a strategy in which we mimic the geotectonic events we find in nature. The latter uses a sculpting approach with convex polyhedra as a carving tool. To this end, several works are presented.While the first option introduces some gains with limits, the second option is a proposal that accomplishes the five required constraints. On the one hand, it can model tunnels, caves and overhangs, and terrain features can be captured with pixel-perfect accuracy. On the other hand, it is not demanding regarding processing and storage requirements and offers scalability. Finally, rendering, physics and dynamic updates can be performed in real-time.As a result, this work represents a significant contribution, offering an integrated solution capable of addressing the most challenging aspects of dynamic terrains. Our approach introduces a novel terrain model comprising diverse data structures and a suite of algorithms designed to capture a wide range of terrain formations accurately. A scene composed of tens of millions of triangles can be continuously updated to the extent of simulating a completely devastated terrain, rendered, and subjected to real-time physics computations involving tens of thousands of physical entities. The proposed model holds great potential for computer graphic applications, particularly in scenarios such as simulators and games, where dynamic landscapes play a paramount role.
  

DOCTORAL DEGREE IN CONSTRUCTION ENGINEERING

• JATIVA GUZMAN, ANDRES: APLICABILIDAD DE LA CENIZA VOLCÁNICA DE BAJA ACTIVIDAD COMO NUEVO RECURSO PARA MATERIALES CEMENTICIOS SOSTENIBLES.
  
  Author: JATIVA GUZMAN, ANDRES
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CONSTRUCTION ENGINEERING
  Department: (DECA)
  Mode: Normal
  Deposit date: 03/04/2024
  Reading date: 29/05/2024
  Reading time: 11:00
  Reading place: Sala C1002 Edifici C1, Escola de Camins (ETSECCPB)- Campus Nord 08034 Barcelona
  Thesis director: ETXEBERRIA LARRAÑAGA, MIREN
  Committee:
       PRESIDENT: MAURY RAMIREZ, ANIBAL CESAR
       SECRETARI: CASANOVA HORMAECHEA, IGNACIO
       VOCAL: GIRÓ PALOMA, JESSICA
  Thesis abstract: Volcanic ash (VA), abundantly available in various regions globally, serves as an effective supplementary cementitious material (SCM) for partially substituting Portland cement (OPC). However, its inherently low reactivity presents a challenge for its broader utilization. This challenge can be overcome by enhancing VA's reactivity via several approaches: 1) employing mechanical and thermal treatments; 2) adding alkali activators; 3) using corrective additives to balance VA's chemical shortcomings; and 4) applying appropriate curing methods to stimulate pozzolanic reactions.According to ASTM C618 standards, VA falls into the Class N category. The study explored various activation strategies, including VA calcination (CVA) at temperatures ranging from 500 to 900 °C, alkali activation using Na2SiO3 (NSi), CaCl2 (CaCl), Na2SO4 (NS), and Na2CO3 (NC) at 1 to 4% dosages (relative to binder weight), and the strategic inclusion of SCMs like lime (L), fly ash (FA), and slag (EC) in amounts of 10, 20, and 30% (relative to VA weight). The curing process's influence was examined under different conditions: moist and heated environments (40 and 70°C for 3 days). The best mortar mixes underwent evaluations for compressive strength at intervals of 7, 28, and 90 days, alongside assessments of physical characteristics (e.g., porosity, water absorption, density) and microstructural properties. The mortars' durability was further gauged through shrinkage and acid resistance tests (against HCl, H2SO4, HNO3).For mortars comprising 35% VA (VA35) and subjected to moist curing, calcining VA at 700 °C coupled with a 20% lime addition resulted in achieving mortars boasting a peak strength of 49 MPa at 28 days, alongside a 9% reduction in water absorption compared to mortars with unmodified VA (VA35). Similarly, employing alkali activators, particularly NSi and CaCl at 1% and 2% dosages respectively, led to mortars demonstrating superior mechanical and physical properties.In mortars with a 50% VA content, the optimal alkali activator dosages were identified as 2% for NSi and 1% for CaCl. The addition of 20% FA and 10% EC emerged as the most effective corrective additives. Thermal curing (70°C for 3 days) significantly boosted early strength gains, curtailed mortar shrinkage, and enhanced resistance to H2SO4, especially notable in mortars prepared with CVA and 1% CaCl. Notwithstanding, at the 90-day mark, moist chamber curing was found to facilitate greater strength increases. A specific mix utilizing mixed activation (1% CaCl with CVA and 10% EC) notably outperformed, achieving 56 MPa, which is a 32% improvement over mortars with untreated VA (VA50). The presence of hydrated phases (C-S-H/C-S-A-H) and minerals such as portlandite, strätlingite, kuzelite, and Friedel's salt attested to the mortars' commendable performance.For mortars containing 75% VA, the best results were achieved with 2% NSi and 1% CaCl as activators, and the addition of 10% FA and 10% EC as correctives additives. Under moist curing, a mixed-activated mortar (1% CaCl-CVA-10%EC) exhibited the highest compressive strength at 90 days, reaching 44 MPa¿a 29% increase over mortars with untreated VA (VA75). Thermal curing expedited early strength development, minimized shrinkage, and bolstered resistance to H2SO4, along with improving porosity and water absorption rates, with the exception of CaCl-containing mortars. Notably, the VA75 mix showed limited portlandite formation and an absence of strätlingite.This investigation confirms the feasibility of achieving satisfactory compressive strengths in mortars with high VA content. Furthermore, by leveraging the studied activation and curing techniques, it's possible to tailor the mortar mix for specific applications, optimizing for properties such as minimal shrinkage, reduced water absorption, enhanced early-age strength, or heightened resistance to particular acid exposures.
  
• LIPA CUSI, LEONEL: Metodología numérica automatizada para la evaluación de la respuesta dinámica de construcciones prehispánicas de piedra de junta seca en el Perú.
  
  Author: LIPA CUSI, LEONEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CONSTRUCTION ENGINEERING
  Department: (DECA)
  Mode: Change of supervisor
  Deposit date: 03/04/2024
  Reading date: 20/05/2024
  Reading time: 16:00
  Reading place: Pontificia Universidad Católica del Perú- 9:00h (Lima). Zoom Reunión:https://pucp.zoom.us/j/94161428415?pwd=YzZrSUQza01NQWkwY1R5UEg2MlZIdz09
  Thesis director: PELA, LUCA | TARQUE, SABINO NICOLA
  Committee:
       PRESIDENT: GOICOLEA RUIGÓMEZ, JOSÉ MARÍA
       SECRETARI: ROCA FABREGAT, PEDRO
       VOCAL NO PRESENCIAL: SANDOVAL MANDUJANO, CRISTIAN
       VOCAL NO PRESENCIAL: SANTA CRUZ HIDALGO, SANDRA CECILIA
       VOCAL NO PRESENCIAL: SALOUSTROS, SAVVAS
  Thesis abstract: The study and the conservation of stone heritage is a global concern, mainly when these constructions are in seismic zones. Due to its great cultural and historical diversity, Peru has many stone constructions in different archaeological sites, covering different construction typologies. Unfortunately, many of these constructions have not yet been structurally evaluated, so their structural behaviour is unknown. In addition, there is no classification of the stone structural typologies (taxonomy), so the different characteristics of existing constructions are unknown. One way to study the non-linear dynamic behaviour of these stone structures is to use a rigorous -but fast- numerical methodology to adequately reproduce the different failure mechanisms based on the dynamics of rigid bodies within the finite element method.Then, this work presents a taxonomic classification of prehispanic stone constructions in Peru, derived from a field study, as the first contribution. Based on this taxonomy, several archaeological sites in Puno and Cusco were classified, and the most common typologies of these regions were identified. The research also proposes novel algorithms developed in Python to obtain the geometric model of dry-joint stone structures using images taken by a camera, a mobile phone, or an existing photograph (including identification of stones and joints, named image segmentation). These routines allow the creation of a 3D model of each block (stone), assembling them, and exporting them to a finite element program for further evaluation.Regarding developing a numerical methodology, the dynamic of rigid bodies within the finite element method is proposed here. Each stone block is considered a rigid body interconnected with other blocks through nonlinear interfaces. This methodology was validated using Abaqus, based on the results of experimental tests developed in this thesis. The experimental campaign was carried out on three walls built with concrete blocks, simulating the geometry of the Inca structures. The walls were built on a tilting table and tested by rotating them out of the plane of the wall. Then, numerical models of the tests were developed by considering each stone as a rigid body and calibrating the contact properties to simulate the experimental behaviour correctly. The numerical results in weight, collapse angle, relative displacements at different points of the structure and collapse mechanisms were very similar to those obtained in the experimental campaign.As a case study, a section of an Inca stone wall from Sacsayhuaman, Cusco, was numerically evaluated using various seismic records. The complete geometric model of the stone wall was automatically obtained using the Python routines. Furthermore, discrete element particles represented the soil behind the wall. The properties of the numerical model were obtained from the experimental campaign, and the predominant frequencies of the structure were obtained using the vibration approach. As a result, the structure can adequately support these seismic records scaled up to a peak acceleration of 0.1 g. However, it suffers significant residual displacements for scaled records greater than 0.2 g.The proposed numerical methodology allows the rigorous evaluation of dry-jointed stone structures, knowing if the structure should be intervened to ensure its functionality. Therefore, it is expected that the results of this research will be used to study other stone constructions, opening possibilities for improving the methodology for different structural configurations.
  

DOCTORAL DEGREE IN ELECTRONIC ENGINEERING

• PUSAY VILLARROEL, BENJAMÍN ANDRÉS: Fabricación de células solares con absorbedores inorgánicos emergentes y contactos selectivos
  
  Author: PUSAY VILLARROEL, BENJAMÍN ANDRÉS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ELECTRONIC ENGINEERING
  Department: Department of Electronic Engineering (EEL)
  Mode: Normal
  Deposit date: 17/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: PUIGDOLLERS GONZALEZ, JOAQUIN | ORTEGA VILLASCLARAS, PABLO RAFAEL
  Committee:
       PRESIDENT: ASENSI LÓPEZ, JOSÉ MIGUEL
       SECRETARI: PLACIDI, MARCEL JOSE
       VOCAL: RIERA LORENTE, SERGI
  Thesis abstract: Silicon is abundant in nature and plays a predominant role in the photovoltaic industry for generating electrical energy. However, the current cost of this solar technology remains high, especially at a commercial level where efficiency reaches 22%. One strategy to reduce the cost of solar energy production involves enhancing the efficiency of solar modules. This can be achieved by integrating new techniques and technologies into the manufacturing processes of the industry, along with the use of abundant and low-toxic materials.Multi-junction solar cells (tandem) enable the integration of two different technologies to leverage their respective qualities as light absorbers, thereby enhancing their electrical performance. Additionally, these cells facilitate the simplification and adoption of new techniques during the manufacturing process. With its Band Gap of 1.1eV, silicon stands out as an excellent candidate for the bottom cell in multijunction or tandem solar cells.The objective of this thesis is to enhance the efficiency of silicon solar cells by utilizing them as multijunction bottom cells to create tandem solar cells. This will be achieved by incorporating a front solar cell based on emerging technologies.To achieve this objective, the introduction is developed, which includes a brief state-of-the-art overview of silicon-based solar cells, the development of tandem solar cells, and the most promising alternatives for emerging inorganic absorbers with adjustable Band Gap, such as kesterites or chalcopyrites (e.g., CuGaSe). The theoretical analysis enables the selection of technologies and processes developed in available laboratories.The application of robust methods for depositing selective contacts in silicon is under investigation. This process aims to prepare the silicon for the thermal and chemical processes involved in the growth of inorganic solar cells, such as kesterites or CGS. This approach enables the development of a robust, efficient, and long-term multijunction solar cell.In a second section, the study on semi-transparent selective contacts for solar cells with inorganic absorbers, such as kesterites or CGS, is presented. The goal is to obtain a compatible substrate for tandem solar cells. As an alternative to traditional CdS for the ETL, we propose the use of Al2O3/TiO2/Mg,i:ZnO layers. Additionally, the potential of enhancing its characteristics by adding polymers (PEI, Glycine) as dipoles is studied.Regarding the hole transport layer (HTL), a semi-transparent alternative to the opaque MoSe2 layers was developed using V2Ox.This layer functions as an interface between the absorber and the transparent electrode (TCO). The incorporation of this layer into kesterite solar cells yielded a semi-transparent device with promising haracteristics, and its application has a significant impact on the efficiency of solar cells.In the last section, a manufacturing process for tandem solar cells is proposed, utilizing Silicon technology as the bottom cell and emerging inorganic solar cells, such as kesterite and CGS, as the top solar cell. Strategies are studied to create a monolithic two-terminal (2T) device, with attention to preserving the physical and electrical characteristics of each device throughout the manufacturing process and during chemical and thermal exposures. Additionally, a study is presented on strategies for the formation of a monolithic device with three interdigitated back contact (IBC) type terminals, which is crucial for obtaining efficient and stable devices in the long term.Through the implementation of these techniques, we anticipate contributing to the research and development of tandem solar cells based on abundant and sustainable materials. This advancement could significantly accelerate the global adoption of solar energy as a clean and renewable source.
  
• RALLIS, KONSTANTINOS: Novel Nanoelectronic Circuits and Systems
  
  Author: RALLIS, KONSTANTINOS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ELECTRONIC ENGINEERING
  Department: Department of Electronic Engineering (EEL)
  Mode: Normal
  Deposit date: 13/03/2024
  Reading date: 09/05/2024
  Reading time: 11:00
  Reading place: ETSETB - Multimedia room Building B3 at Campus Nord UPC
  Thesis director: RUBIO SOLA, JOSE ANTONIO | SIRAKOULIS, GEORGIOS
  Committee:
       PRESIDENT: JIMÉNEZ JIMÉNEZ, DAVID
       SECRETARI: ABADAL CAVALLÉ, SERGI
       VOCAL: CUCU LAURENCIO, NICOLETA
  Thesis abstract: Lately, in the rise of the era of 2D materials, Graphene is one of the materials that has been extensively investigated for its possible integration in computing devices and thus computing circuits. This is mainly attributed to its very wide set of appealing properties. The combination of its electronic properties with others, such as mechanical, optical or chemical properties, can extend the range of use of computing devices and lead to groundbreaking interdisciplinary applications. However, this integration of Graphene in switching and computing elements is not easy. In this dissertation, the Non-Equilibrium Green's Function method (NEGF), along with the Tight Binding Hamiltonians, are fitted on experimental data from fabricated Graphene devices. Although as a computational method, NEGF is appropriate for the simulation of small-scale devices in the regime of nanometers, its ability to be efficiently expanded for the description of larger devices is presented. The aforementioned electronic properties of the material are highly related to its shape and structure. Consequently, it requires a very precise fabrication method that can guarantee the minimum presence of defects on the Graphene grid. For that reason, the effect of defects is deeply investigated. The NEGF method is further enhanced in order to be able to incorporate lattice defects. The most common lattice defects are included, meaning the single and double vacancy. A framework has thus been created, so that for the first time the user can select areas of interest on the grid, in which the defects will be concentrated. Those concentrations can also be variable. Moreover, an extensive study is conducted on defective grids with different concentrations of single and double vacancies. The investigated grids are non-rectangular and have regions with different widths. The effect of those vacancies on the electronic properties of Graphene is investigated, and more specifically their effect on the conductance and the energy gap of the device, as well as the effect on circuit-centered characteristics such as the leakage current and ON/OFF current ratio. Having a functional, robust, versatile, and accurate model, the focus of this thesis is extended to the level of circuits. The model is imported into SPICE through Verilog-A. In this part, the thesis emphasizes on the investigation of the switching capabilities of L-shaped Graphene Nanoribbons (GNRs). These structures have been proven to be able to operate as switches, without the use of a back gate, and here, the properties that are dependent on their dimensions are explored and optimized for the first time. The optimized structures are then used for the realization of a set of computing topologies. Initially, a novel area-optimized 2-branch comb-shaped topology is introduced for the realization of a universal computing set that consists of an AND, OR, NOT gate, and a Buffer. All these logic operations can be mapped on the same topology through appropriate biasing. Then, an extension of this, the 3-branch comb-shaped topology is proposed, which is able to operate as a 2-XOR, 3-XOR and 3-MAJ gate. The circuit of a 1-bit full adder, is also presented. For the evaluation of the performance of the topologies, several related metrics are employed such as the area, delay, power dissipation and the power-delay product. The operation of these topologies relies of the principles of Pass Transistor Logic (PTL) and reconfigurable computing. Finally, in an attempt to go beyond the conventional Boolean logic, the compliance of Graphene with Multi-Valued Logic (MVL) circuits and applications is investigated. The ability of a Graphene Quantum Point Contact (G-QPC) device to encode the digits of the radix-4 numeral system is presented and as a proof of concept, the operation of an arbitrary radix-4 adder is explained.
  

DOCTORAL DEGREE IN ENVIRONMENTAL ENGINEERING

• KILIÇ, EYLEM: Advancing the use of waste streams in plastic composites
  
  Author: KILIÇ, EYLEM
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ENVIRONMENTAL ENGINEERING
  Department: (DECA)
  Mode: Article-based thesis
  Deposit date: 18/03/2024
  Reading date: 30/05/2024
  Reading time: 12:00
  Reading place: Place: ETSECCPB UPC, Campus Nord Building C1. Classroom: 002 C/Jordi Girona, 1-3 08034 Barcelona
  Thesis director: PUIG VIDAL, RITA | FULLANA PALMER, PERE
  Committee:
       PRESIDENT: MÉNDEZ GONZÁLEZ, JOSÉ ALBERTO
       SECRETARI: GASSO DOMINGO, SANTIAGO
       VOCAL NO PRESENCIAL: EL BACHAWATI, MAKRAM
  Thesis abstract: The leather industry faces global challenges related to its sustainability credentials due the significant waste generated throughout the leather production processes. In the context of contemporary environmental policy, which is increasingly focused on sustainable production and consumption, the need to understand and mitigate environmental impacts associated with leather has become a strategic and economic imperative. In this respect, a comprehensive "gate-to-gate" life cycle assessment (LCA) was conducted following the newly released Leather Product Environmental Footprint Category Rules (PEFCR). The analysis aimed to evaluate the environmental impacts of leather production, with a specific focus on New Zealand's leather production industry, mainly due to its agriculturally oriented economy and large size of livestock sector.This thesis builds upon this foundation by addressing the issue of solid waste in the leather industry. Therefore, a waste valorization strategy was investigated to convert unavoidable waste into valuable resources through the production of new, value added composites, which involves incorporating leather waste (BF) into virgin and recycled high-density polyethylene (HDPE). The focus of this thesis is to analyze environmental impact of these novel composites, to improve the implementation of circular economy principles, within the context of their use in automotive bumper production. The environmental impact of these novel composites was compared to conventional polypropylene (PP), bumpers, by performing a cradle-to-gate life cycle assessment (LCA). The thesis also aims to provide a contribution to LCA methodology applied to composite materials, by adopting various functional units, such as mass, volume, and the volume of raw material fulfilling a specific impact strength requirement.The in-depth analysis of mechanical and thermal properties of the BF/HDPE composites highlights the composite¿s potential for industrial applications that require high mechanical strength and low thermal conductivity. The incorporation of leather waste not only enhances material properties, but also contributes to environmental sustainability by converting unavoidable waste into a value added product. The environmental assessment, adopting a cradle-to-gate LCA with various functional units, indicates that composites made from recycled HDPE and leather waste have a lower environmental impact than those from virgin materials. The only exception is when the material's impact strength is a key factor in the functional unit, due to the higher impact strength of HDPE-BF composites. In all cases, increasing the content of recycled materials in the bumpers increases its environmental performance, supporting the advancement of circular economy principles in the automotive sector.The research highlights the significance of choosing an appropriate functional unit, based on specific applications such as automotive bumpers, in comparing the environmental footprint of innovative composite materials with that of traditional materials. Broadening the scope of evaluation to include various functions yields a more realistic scenario, but it leads to higher uncertainties in the results as well.
  

DOCTORAL DEGREE IN GEOTECHNICAL ENGINEERING

• BISCARO, CATERINA: 3D FEM meso-level analysis of sulphate attack in concrete: new results and developments using parallel HP computing
  
  Author: BISCARO, CATERINA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN GEOTECHNICAL ENGINEERING
  Department: (DECA)
  Mode: Change of supervisor
  Deposit date: 16/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: CAROL VILARASAU, IGNACIO | XOTTA, GIOVANNA
  Committee:
       PRESIDENT: SALOMONI, VALENTINA
       SECRETARI: PRAT CATALAN, PERE
       VOCAL: LIAUDAT, JOAQUÍN
       VOCAL: MAROTTI DE SCIARRA, FRANCESCO
       VOCAL: CIANCIO, DANIELA
  Thesis abstract: When concrete is subject to an environment characterised by a high humidity index and rich in sulphate ions, a concrete degradation process may be initiated due to External Sulphate Attack (ESA). The sulphate penetrating into the concrete activates a series of chemical reactions that lead to the formation of secondary ettringite, which may cause non-uniform volumetric expansions that may in turn generate cracking and ultimately culminate in the disintegration of the sample. Because the cracking may in turn facilitate sulphate penetration, ESA may be considered a coupled chemical-mechanical problem. In this study, the numerical analysis of ESA is conducted using the Finite Element Method by considering the specimen at the meso-level composed of larger aggregates embedded in a mortar matrix. Standard continuum finite elements are used to discretise the aggregates and the mortar. Zero-thickness interface elements are inserted along all the aggregate-mortar and selected mortar-mortar contacts to represent potential cracks. The diffusion-reaction of sulphate ions (chemical problem) is formulated following Tixier and Mobasher (2003) and Idiart et al. (2011b). Regarding the mechanical problem, the continuum elements are considered linear elastic, while the interface elements behave according to an elasto-plastic law incorporating concepts of fracture mechanics which was initially developed by Carol et al. (1997) and later extended for 3D analysis by Caballero et al. (2006).The first part of this thesis deals with the verification and use of DRAC5, a completely parallelised version of the in-house code developed within the materials mechanics group (MECMAT) of the Universitat Politècnica de Catalunya (UPC) which now incorporates MPI and PETSC libraries as well as HDF5 i/o files. This new version of the code, which is used to solve both the mechanical problem and the chemical problem through a staggered scheme, has allowed the analysis of new and more challenging 3D studies, producing realistic results that reflect the 'onion peeling' cracking pattern, similar to what has been observed in the laboratory and in previously studied 2D cases (Idiart, 2009). The second part of the thesis, deals with the development of new numerical solving techniques applicable to this type of mesh. In particular, a solution technique based on substructuring and the Schur complement is applied to the analysis of specimens comprising elements of the continuum exhibiting linear elastic behaviour and interface elements characterised by non-linear (elasto-plastic) behaviour. This new technique, which reduces substantially the number of degrees of freedom that need to be considered during the iterative process, has been preliminarily implemented in DRAC4, a simpler series version of the code, and is tested showing great advantages in terms of solution time for a range of 2D application examples. The development of a new formulation using rigid-plastic interfaces is also initiated. This formulation uses relative degrees of freedom at each pair of interface nodes, and leads to the resolution of a Linear Complementarity Problem. This development allows a further reduction in the degrees of freedom of the problem by only considering the nodes of the interface elements involved in the fracture process.
  

DOCTORAL DEGREE IN MATERIALS SCIENCE AND ENGINEERING

• GORDON POZUELO, SANDRA: Mechanical integrity of coated PcBN systems: Mechanics and mechanisms involved under service-like conditions
  
  Author: GORDON POZUELO, SANDRA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN MATERIALS SCIENCE AND ENGINEERING
  Department: (CEM)
  Mode: Article-based thesis
  Deposit date: 19/02/2024
  Reading date: 10/05/2024
  Reading time: 11:00
  Reading place: EEBE (Escola d'Enginyeria Barcelona Est), Aula A2.14, planta 2, Campus Diagonal-Besòs
  Thesis director: LLANES PITARCH, LUIS MIGUEL | ROA ROVIRA, JOAN JOSEP
  Committee:
       PRESIDENT: MARI, DANIELE
       SECRETARI: FARGAS RIBAS, GEMMA
       VOCAL: BOTERO VEGA, CARLOS ALBERTO
  Thesis abstract: Polycrystalline cubic boron nitride (PcBN) is a composite competitive cutting tool material that excels performance when machining difficult-to-cut materials (e.g. hardened steels, superalloys, etc) due to its exceptional mechanical properties. In practice, PcBNs are coated with a ceramic film to prevent and prolong the onset of tribo-oxidation and abrasive wear. Although there is not a unique consolidated opinion regarding the benefits of coatings in PcBN, most of the bibliography agrees on their use when involving hard turning operations. Most of the research address the tool performance and wear mechanisms, whereas information involving materials science aspects of PcBN and coated PcBN tools, on the basis of understanding microstructure ¿ mechanical properties correlations, is quite limited. In this regard, this thesis focusses on studying hardness, fracture toughness and wear resistance as they are key mechanical properties controlling the mechanical integrity and reliability of the tool, which are related with the contact response, fracture resistance (e.g. premature chipping) and effective tool life, respectively. Four distinct substrates of the coated PcBN grades are studied and first characterized, including the development of characterization and testing protocols. In doing so, focus ion beam tomography and three-dimension (3D) image reconstruction was implemented to study the bulk microstructural characteristics of a PcBN grade with high cBN content and metallic binder. It was found to be a powerful and useful method to gain in-depth knowledge and understanding the microstructural characteristics of PcBN composite materials, additionally to those gathered by conventionally 2D method. The study then focuses on the assessment of the micromechanical properties of PcBN composite materials, as they are known to be key for optimizing their performance through microstructural design. High-speed nanoindentation is successfully implemented to characterize and correlate microstructure with local mechanical properties of such hard and stiff composite materials; where two different methodologies, 1D and 2D Gaussian, are used for statistically deconvoluting the data. It is found that the harder PcBN grade is clearly related with the high cBN content. A scaled-up method was employed to evaluate the contact response of uncoated PcBN grades. The higher cBN content and metallic binder grade, exhibits higher resistance to crack nucleation and a more gradual transition through different damage scenarios due to the concomitant increase of hardness and fracture toughness of this grade. Regarding fracture toughening mechanisms, crack path changes from propagation across the ceramic binder to transgranular fracture through cBN particles, as the cBN content increases. Very interesting, fracture toughness is enhanced by crack interaction with intrinsic sub-grained or twin boundaries within the individual cBN particles as well as by crack deviation through nano cBN particles dispersed in the binder. Afterwards, research was aimed to characterize coated PcBN (with different chemical nature and bias voltage), mainly in terms of coating adhesion strength and mechanical integrity of bulk coated systems as a function of the PcBN substrate microstructural assemblage. Mechanical response of the coated system, assessed by using Rockwell C indentation technique and scratch testing, is strongly dependent on the underneath substrate microstructural assemblage; and therefore, its different intrinsic hardness-toughness correlation. Finally, TiAlN-coated PcBN inserts were used to mill a hardened cold work tool steel. It was proposed as an exploratory study of milling performance of coated PcBN systems to assess the onset of coating failure without involving the emergence of other wear phenomena (e.g. thermally-driven ones).
  
• MARTIN SAINT-LAURENCE, PABLO: Constitutive modeling of ultrafine-grained refractory high-entropy alloys obtained by powder metallurgy
  
  Author: MARTIN SAINT-LAURENCE, PABLO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN MATERIALS SCIENCE AND ENGINEERING
  Department: (CEM)
  Mode: Normal
  Deposit date: 17/04/2024
  Reading date: 28/05/2024
  Reading time: 11:30
  Reading place: EEBE (Escola d'Enginyeria Barcelona Est) Sala Polivalent de l'Edifici A, Edifici A, planta baixa, Campus Diagonal-Besòs
  Thesis director: CABRERA MARRERO, JOSE MARIA
  Committee:
       PRESIDENT: TORRALBA CASTELLÓ, JOSE MANUEL
       SECRETARI: LLORCA ISERN, NURIA
       VOCAL: CARREÑO GOROSTIAGA, FERNANDO
  Thesis abstract: Refractory high-entropy alloys (RHEAs) prepared by mechanical alloying followed by spark plasma sintering usually outweigh the high-temperature mechanical behavior of as-cast counterpart alloys. Despite that, few studies have been conducted in order to understand their deformation mechanisms associated with these alloys and their particular microstructures (ultrafine grain size and considerable presence of secondary phases). The present work reports the synthesis, the microstructural characterization, and the constitutive modeling the AlCrxFeMoNbTiV2 (x = 0.15, 0.4, 0.8) RHEAs prepared by powder metallurgy, aiming to contribute to the comprehension of the deformation mechanisms behind the high-temperature mechanical behavior of RHEAs obtained with this fabrication route, as well as of the composition-microstructure-properties of RHEAs.In order to do so, the study was divided into three parts. In the first one, the effect of composition and milling time over themicrostructural and particle evolution of the powder was investigated. In the second part, the effect of Cr content and of a heat treatment over phase formation, microstructure, and grain size was investigated. In the third part, the samples were subjected to compression testing between 950 °C and 1100 °C and between 0.0005 s-1 and 0.01 s-1 to obtain the constitutive equations of the peak stress. Additionally, the microstructure of some of the deformed samples was characterized to find microstructural hints associated with the different potential softening and deformation mechanisms. During the milling study, it was observed that most of the changes occurred during the firsts 50 h, resulting in an average particle size of 7 µm and a nanostructured bcc+hcp microstructure. Except for Mo, none of the constituent elements considerably affected the microstructure or the particle size of the milled powders. The as-sintered samples, fabricated using powder milled for 50 h, successfully presented an ultrafine-grained and multiphase microstructure, constituted by a V,Mo-rich bcc matrix, accompanied by Fe,Nb-rich Laves phases, Al2O3 particles, and Ti,Nb-rich carbides. For reference, a hardness of 1124 HV0.3 was obtained in the as-sintered samples. The average grain size of the matrix phase decreased from 0.40 µm to 0.21 µm with further Cr content; however, the high-temperature mechanical properties were not affected. On the other hand, after the heat treatment, the average grain size increased up to 1.5 µm without affecting the phase equilibrium though. In opposition to the Cr content, the heat treatment enhanced the yield strength in a considerable manner: a specific yield strength of 98 MPa·g-1·cm3 at 1000 °C was obtained in these samples, three times that of the as-sintered sample. Regarding the constitutive modeling, the power law excellently fitted the experimental data, resulting in an exponent of 2.45, indicating that grain boundary sliding governed the high-temperature deformation of the studied alloy, just as it does in ultrafine-grained size traditional alloys. Additionally, an elevated activation energy of 527 kJ·mol-1 was obtained, associated either with a high softening resistance as well as with the considerable presence of secondary phases. In the case of the heat-treated samples, dislocation climbing and glide seemed to govern the deformation (at least at 1000 °C), explaining the enhanced strength, attributed to the hindered grain boundary mobility due to the larger grain size.
  

DOCTORAL DEGREE IN MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING

• CHEN, JIAN: EFFECTS OF CAVITATION ON THE WAKE CHARACTERISTICS BEHIND BLUNT TRAILING EDGE HYDROFOILS
  
  Author: CHEN, JIAN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING
  Department: Department of Fluid Mechanics (MF)
  Mode: Normal
  Deposit date: 22/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: ESCALER PUIGORIOL, FRANCESC XAVIER
  Committee:
       PRESIDENT: HIDALGO DÍAZ, VICTOR HUGO
       SECRETARI: CASTILLA LOPEZ, ROBERTO
       VOCAL: ZHANG, DESHENG
  Thesis abstract: The recent developments in hydraulic machinery will increase the possibility of damage resulting from cavitation and/or vortex-induced vibrations. Yet, many researchers have shed light on the vortex street flow and the associated vortex-induced vibration in cavitating-free regimes, but less attention has been paid to the presence of cavitation. In the present study, the effects of cavitation on the vortex street flow behind a blunt trailing edge hydrofoil and its interaction with the vortex-induced vibration have been investigated. This will help to understand the mechanisms involved and to predict the dynamic of vortex-induced vibration with the presence of cavitation, allowing further control of this complex phenomenon in hydraulic machinery and systems.Thus, numerical solvers have been developed that are capable of accounting for the cavitating vortex street flow behind bluff bodies which have been validated and verified using some benchmark cases. Then, the effects of the fluid compressibility in the vortex street flow behind the wedge have been determined. Moreover, a series of numerical studies on cavitating vortex street flow behind a blunt trailing edge hydrofoil NACA 0009 have been conducted by predicting the boundary layer transition. As a result, the effects of cavitation on flow dynamics and its interaction with vortex-induced vibration have been examined.The impacts of fluid compressibility on the dynamics of the cavitating wake flow have been found to depend on the frequency range. At low frequencies, the effects of fluid compressibility are minimal and can be disregarded. On the other hand, fluid compressibility has been observed to amplify spectral energy at high frequencies. Interestingly, it has been found that almost identical numerical results with and without fluid compressibility are obtained in terms of predicted mean pressure profiles, dominant vortex shedding frequencies, and instantaneous and mean void fraction fields, which suggests that the compressibility effects on cavitating vortex shedding can be neglected. For the cavitating vortex street flow behind a blunt trailing edge hydrofoil NACA 0009, high-fidelity numerical simulations have been established in the current thesis. Based on the results, it has been observed that cavitation has a significant impact on the wake flow dynamics, notably increasing the shedding frequency of the primary vortices. Additionally, cavitation growth leads to increased hydrodynamic loads on the hydrofoil surface. Furthermore, cavitation development enhances the advected velocity of the vortices while decreasing the streamwise inter-vortex spacing. Both factors are believed to contribute to the increase of the vortex shedding frequency while the reduction of streamwise inter-vortex spacing tends to dominate this increase.The numerical results related to cavitating vortex street flow behind a blunt trailing edge hydrofoil NACA 0009 subjected to forced oscillation have shown that the induced dynamic response due to the oscillation is influenced by the presence of cavitation. In the lock-in regime, cavitation appears to widen the upper bound of this regime and cause a decrease in the added moment of inertia and an increase in the added damping. Moreover, the timing of the vortex shedding changes with the presence of cavitation. On the other hand, the oscillation of the hydrofoil affects the dynamics of cavitation in terms of cavitation inception and cavity length. Generally, the cavitation inception number gradually increases with the forced oscillation frequency. Meanwhile, approaching the bounds of the lock-in regime will cause local decreases in cavitation inception numbers. Besides, the length of the cavitating wake is influenced by the variation of the oscillation frequency, and the maximum cavitating wake length occurs under stationary conditions.
  

DOCTORAL DEGREE IN NETWORK ENGINEERING

• CEPEDA PACHECO, JUAN CARLOS: Contribution to the enhancement of IoT-based application development and optimization of underwater communications, by artificial intelligence, edge computing, and 5G networks and beyond, in smart cities/seas
  
  Author: CEPEDA PACHECO, JUAN CARLOS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN NETWORK ENGINEERING
  Department: Department of Network Engineering (ENTEL)
  Mode: Normal
  Deposit date: 22/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: DOMINGO ALADREN, MARIA DEL CARMEN
  Committee:
       PRESIDENT: LLORET MAURI, JAIME
       SECRETARI: REMONDO BUENO, DAVID
       VOCAL: HUERTA, MÓNICA KAREL
  Thesis abstract: 6G networks have emerged as a revolutionary breakthrough, promising ultra-fast and reliable connectivity that redefines the way we interact with the digital world. This new generation of networks not only drives communication between devices but is also the backbone of the Internet of Things. In addition, the learning and adaptive capabilities of Artificial Intelligence systems are driving process automation and efficiency. Similarly, Edge Computing complements this landscape by decentralizing data processing, bringing computing capacity closer to the sources of information. This allows for reducing latency and improving efficiency byprocessing data in real-time, driving critical applications that require instantaneous responses.This thesis focuses on two important points: 1) Improving the efficiency of applications in smart cities, and 2) Enhancing the efficiency of underwater communications in smart coastal cities by applying artificial intelligence, edge computing, and 5G and beyond. To achieve these objectives, an exhaustive study of the existing literature on 5G and beyond networks, smart cities, and artificial intelligence has been carried out. In addition, technical documentation to obtain an updated view of the different technologies that enable the development of applications based on 5G and beyond has been analyzed. Aiming to generate newand innovative alternatives in the field of tourism, security, improved underwater communications, and marine discovery that drive promote development to meet the needs of citizens in smart cities and ocean/sea. As a result of this study, the first contribution has emerged. It involves the analysis, design, and implementation of a tourist attraction recommendation system employing a deep learning algorithm tailored for smart cities. The primary objective is to improve how tourist attraction recommendations are made so that they are tailored to the requirements of each visitor in a given city and thereby reduce the time it may take a visitor to search for possible places to visit.The second contribution arises in surveillance and security, which consists of a distraction detection system for the prevention of drowning in aquatic places, developed in a 5G and beyond network environment. For this goal, an approach of surveillance cameras capturing images of people in charge of minors in swimming pools or beaches was proposed; and employing an ML algorithm (convolutional neural networks) to classify the type of distraction that a person in charge of a minor may have.Finally, the third contribution is presented, called reinforcement learning and mobile edge computing for 6G-based underwater wireless networks. In this approach, a submerged edge mobile computing architecture is presented in which an AUV is used as a mobile platform (MEC), in addition, several local AUVs equipped with computational resources that collect tasks from sensor nodes and can make the decision to process them locally or partially or fully offload them to the mobile edge computing AUV device. To this end, an algorithm based on deep reinforcement learning (DDPG) is proposed for trajectory control, task offloadingstrategy, and computational resource allocation, combined with mobile edge computing and AUVs to improve underwater communication; aiming to minimize the sum of maximum processing delays and energy consumption during the whole process of executing a task.The contributions presented in this doctoral thesis are of singular importance, since to date they continue to be innovative. The contributions presented not only represent significant advances in their respective areas but also lay the groundwork for future research and developments in smart city construction and underwater communications optimization, thereby reinforcing the transformative potential of artificial intelligence, edge computing, and advanced wireless networks in these domains.
  
• HAASTRUP, ADEBANJO: Enhanced Dynamic Bandwidth Algorithms for Passive Optical Networks
  
  Author: HAASTRUP, ADEBANJO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN NETWORK ENGINEERING
  Department: Department of Network Engineering (ENTEL)
  Mode: Normal
  Deposit date: 22/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: RINCON RIVERA, DAVID | PINEY DA SILVA, JOSE RAMON
  Committee:
       PRESIDENT: KHALILI, HAMZEH
       SECRETARI: SPADARO, SALVATORE
       VOCAL: PAPAGIANNI, CHRYSA
  Thesis abstract: The telecommunications industry faces rapid changes due to the deployment of ultra-high speed access networks (5G and beyond, fiber-to-the-home), promising unparalleled experiences with high bandwidth and low latency. However, this transition brings challenges. With the surge in smart device numbers and bandwidth demand, optimizing network architecture, management, and resource usage is crucial for cost-efficiency. Passive Optical Networks (PONs) offer efficient broadband access for residential and commercial sectors, with advantages like energy efficiency and robust security and high performance. Leading organizations, such as IEEE and ITU-T, are actively developing standards to increase the capabilities of next-generation PONs. The goal is to meet the demands by implementing innovative mechanisms for efficient management, resource allocation, QoS, energy savings, and low latency.Next-generation PONs have introduced the use of multiple wavelengths based on TWDM techniques. However, managing multiple wavelengths presents challenges, as DBA algorithms need to consider both the time and wavelength dimensions of the network. This follows a Joint Time and Wavelength Scheduling (JTWS) scheme, which requires complex implementation. TWDM-PON also utilizes tunable transceivers in ONUs to switch between wavelengths, but this introduces a delay called Laser Tuning Time (LTT) which is often ignored, but it is an important consideration when designing our DBA algorithms. Additionally, there is a demand to integrate metro and access networks for streamlined telecom infrastructure. Long Reach PON (LRPON) offers a solution by expanding coverage from 20 km to 100 km, enabling high-speed, long-distance data transmission over optical fibers. This reduces the need for central offices, resulting in cost savings. However, the extended reach of LRPONs introduces new challenges, particularly in the area of DBA algorithms. Traditional DBA algorithms like IPACT may not be as efficient for LRPONs due to increased propagation delays and round-trip times (RTT) between the OLT and ONUs. To address these challenges, a novel DBA algorithm called the Distance Weighted DBA (DWDBA) algorithm is proposed.This thesis delves into the limitations of traditional DBA algorithms and proposes novel Enhanced DBA solutions for PONs. Leveraging techniques such as the Longest Processing Time (LPT) scheduling method to minimize queue delays, our DBAs also consider the concept of laser tuning time to bring a practical, real-world approach to our system. The main contributions of this thesis are: - Incorporating the often-overlooked laser tuning time (LTT) concept in our analysis of DBA for TWDM PONs, therefore obtaining more realistic results. - Introducing an innovative algorithm for PONs employing LPT to minimize queue delay and enhance throughput, resulting in a notable reduction (up to 73%) with respect to the queue delay when compared to IPACT. - Developing a Distance Weighted DBA (DWDBA), specifically tailored for LRPONs, aimed at preventing the penalization of ONUs located farther from the OLT. This results in improving up to 30% and 10% the queue delay and throughput, respectively, over IPACT.The effectiveness of these proposed algorithms is rigorously evaluated through comprehensive simulations, demonstrating their potential to meet the demands of future networks.
  

DOCTORAL DEGREE IN OPTICAL ENGINEERING

• BALLESTA GARCIA, MARIA: Propagation of polarized light through turbid media: Application of lidar technology in foggy environments
  
  Author: BALLESTA GARCIA, MARIA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN OPTICAL ENGINEERING
  Department: Department of Optics and Optometry (OO)
  Mode: Normal
  Deposit date: 22/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: ROYO ROYO, SANTIAGO
  Committee:
       PRESIDENT: ARTEAGA BARRIEL, ORIOL
       SECRETARI: VILASECA RICART, MERITXELL
       VOCAL: BIJELIC, MARIO
  Thesis abstract: In recent times, there has been a growing interest in LiDAR imaging systems for outdoor applications involving computer vision, such as automotive systems, surveillance, and robotics. LiDAR sensors have the ability to capture 3D data, that is, the geometry (volume, distances) of the scenes involved, complementing the 2D projections of scenes available in conventional cameras. However, their limited tolerance to adverse weather conditions, particularly fog, stays as one of the obstacles that hinders their complete settlement. This Thesis aims to evaluate the potential of utilizing the polarization properties of light and the digitization of the signal to improve the system¿s imaging capabilities in such challenging conditions. Additionally, our research offers valuable insights in the domain of imaging through fog. Understanding the interaction of polarized light with turbid media and recognizing the importance of the targets¿ polarimetric properties within the imaged scene is essential for optimizing the performance of polarimetric imaging systems.To achieve our goal, a preliminary investigation to examine the characteristics of polarimetric imaging through fog is undertaken. Our findings indicate that polarimetric imaging modes provide higher contrast compared to intensity-based imaging modes, facilitating the identification and segmentation of different targets. Additionally, experimental characterization of the depolarizing behavior of light through fog is conducted for both reflection and transmission imaging modes. The results suggest that, in this scenario, light behavior falls within the scattering regime of the polarization memory effect, with a significantly reduced depolarization in circularly polarized beams when compared to linearly polarized ones. To the best of our knowledge, this Thesis quantifies for the first time the differences between the performance of both polarization modes in fog conditions. Next, a Monte Carlo-based model is developed to meet the requirements of our LiDAR prototype. Considering the resource-intensive nature of experiments conducted in fog conditions and the dynamic nature of fog, the model¿s ability to accurately simulate the physics of the problem, including a realistic fog environment, helps to guide the definition of the future experimental actions. Subsequently, the model is utilized to simulate and analyze various aspects relevant to the design of the system, including polarization configurations, interactions with targets, and irregularities in the media (in practice, generalizing the scattering media beyond fog to e.g. sand or smog), together with the characteristics of the acquired signal. Finally, this Thesis presents a novel polarized LiDAR imager prototype and evaluates its performance in fog conditions. It conclusively shows that using circularly polarized light and a cross-configuration detection setup significantly improves system performance in such scenarios. This system effectively tackles challenges induced by scattered light, reducing saturation effects from backscattering, mitigating scattering noise in point clouds, and enhancing target detection, especially for highly reflective surfaces like metallic targets. This approach offers an innovative, straightforward, and efficient method for signal stabilization and enhancement of the point cloud quality by relying on the inherent physics of the problem.
  

DOCTORAL DEGREE IN POLYMERS AND BIOPOLYMERS

• FERRERES CABANES, GUILLEM: Hybrid metal-organic nanoparticles for antimicrobial applications
  
  Author: FERRERES CABANES, GUILLEM
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN POLYMERS AND BIOPOLYMERS
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 03/04/2024
  Reading date: 21/06/2024
  Reading time: 11:00
  Reading place: Sala de Conferències de l' ESEIAAT (Escola Superior d¿Enginyeries Industrial, Aeroespacial i Audiovisual de Terrassa), C/ Colom, 1-11, 08222 Terrassa.
  Thesis director: TZANOV, TZANKO | TORRENT BURGUES, JUAN
  Committee:
       PRESIDENT: PASHKULEVA, IVA HRISTOVA
       SECRETARI: GARRIGA SOLE, PERE
       VOCAL: VASSILEVA, ELENA
  Thesis abstract: Antimicrobial resistance (AMR) is a global health concern, which leads to increased morbidity and mortality, huge economic burden to the healthcare systems and potentially untreatable infections. Due to the inappropriate use of antibiotics, the natural adaptation has been accelerated and bacteria have developed multiple ways to degrade, alter, or expel drug molecules. Besides these resistance mechanisms, bacteria can adhere to surfaces and grow as biofilms ¿ organised assemblies of surface-bound cells, enclosed in a self-produced extracellular polymer matrix (EPM). The EPM holds the pathogens together, enables adhesion to surfaces, and enhances the tolerance to host immune responses and antibiotics compared to free-floating cells. Metal nanoparticles (NPs) have been suggested as a potential solution to fight resistant bacteria due to their strong antimicrobial activity and versatile mechanisms of action. However, inherent toxicity towards mammalian cells and large variation of physical properties are challenges that preclude the clinical application of such materials. In this thesis, metal NPs have been combined with different biomolecules for enhanced biocompatibility, increased antimicrobial efficacy, and enabling new functionalities to mitigate AMR.The first part of the thesis describes the formation of Ag NPs using bioactive macromolecules to produce multifunctional nanostructures. First, the matrix-degrading enzyme (MDE) ¿-amylase was used to reduce Ag(I), yielding NPs with antimicrobial and biofilm-degrading activity towards both gram-positive and gram-negative bacteria. Then, chitosan-Ag NPs were decorated with the quorum-quenching enzyme (QQE) acylase I, which combination was able to kill Pseudomonas aeruginosa, hinder biofilm formation, and inhibit bacterial quorum sensing (QS) based on acyl homoserine lactones (AHLs). Finally, adipic acid dihydrazide (ADH) was grafted on hyaluronic acid (HA) and used to form Ag NPs. The modified polymer (HA-ADH) played a crucial role in the interaction of the NPs with bacterial membranes, assessed using Langmuir isotherms, and reduced the toxicity of Ag towards human cells. In the second part of the thesis, HA-ADH and epigallocatechin gallate (EGCG) were used to produce nanostructured complexes with a scarcely studied antimicrobial Co(II). On one hand, Co(II) formed a complex with the biopolymer, which complex was transformed to antimicrobial nanogels (NGs) using an ultrasonic approach. On the other hand, incubation of EGCG with Co(II) yielded nanostructured metal-phenolic networks (MPN). These cobalt-containing NPs were active towards both gram-positive and gram-negative bacteria, and were able to inhibit biofilm formation due to the capacity of ECGC to disrupt QS. The last chapter of the thesis validates the use of the novel nanomaterials for antimicrobial functionalisation of medical devices. Coating of contact lenses with NGs hindered bacterial colonisation and unspecific absorption of proteins without affecting the optical properties and comfort of the material. Inclusion of MPN NPs in thiolated hyaluronic acid (THA) hydrogels endowed these materials with properties promoting efficient chronic wound treatment. The antibiotic-free hydrogels were able to control the main factors of wound chronicity by inhibiting the activity of deleterious wound enzymes, scavenging reactive oxidative species, and demonstrating pronounced antimicrobial activity, resulting in similar to commercial products wound management efficacy confirmed in vivo.
  
• MARTÍ BALLESTÉ, DÍDAC: Advanced molecular modelling techniques for immunosensor nanointerfaces
  
  Author: MARTÍ BALLESTÉ, DÍDAC
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN POLYMERS AND BIOPOLYMERS
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 13/03/2024
  Reading date: 03/06/2024
  Reading time: 11:30
  Reading place: Sala Polivalent de l'Edifici I, Edifici I, planta baixa, Campus Diagonal-Besòs
  Thesis director: TORRAS COSTA, JUAN | ALEMAN LLANSO, CARLOS ENRIQUE
  Committee:
       PRESIDENT: POATER TEIXIDOR, ALBERT
       SECRETARI: SASSELLI RAMOS, IVAN
       VOCAL: CREHUET SIMON, RAMON
  Thesis abstract: Viruses and their infections have always affected human lives throughout history. Globalization contributed positively to the progress of human society in science and medicine which permited to deal with viruses, but the reality is that the number of infections does not decrease over the years. Globalization itself is here agin one of the main factors, as people move in more densely populated areas, which favors the spread of viruses. Another important factor is the viruses themselves, which over the years have shown a constant evolution that allowed them to adapt to new hosts. For these reasons, human-led efforts such as vaccines, antiviral treatments, sensors etc. are critical tools for human survival, and like viruses, humans must continue to innovate. This thesis focused on providing different understandings of a series of biochemical processes at molecular the level to facilitate the design of plasmonic resonance sensors, currently used for detecting diseases such as cancer, to enable a similar detection improvement in other viruses and diseases such as HIV and SARS-Cov-2.This thesis is divided into two parts, with the first focusing on the characterization related to the HIV virus. Several studies have been carried out using a combination of different molecular simulation techniques, classical dynamics, quantum mechanics and hybrid QM/MM-MD methods. These studies characterize the behavior of the antibody chosen in the design of the sensor, IgG1 , as well as its interactions with the silica surface that compounds the sensor and its orientation once functionalized on top of the surface. Additional studies were performedm focusing on the interaction between the immunoglobulin G and the glycoprotein that forms part of the HIV virus spike, and permited to identify the interactions helping the antibody to attach to the virus for the virus inhibition.In the second part, the same molecular simulation techniques have been used to study the virus which completely changed the world in 2020, SARS-CoV-2 known for the disease COVID19. As this virus was new at the time of the thesis, there was a dramatic lack of knowledge. Molecular modelling techniques were used to study the behavior of the virus spike in presence of heat or solvated in water. Similar studies to the case of HIV-IgG1 were performed between SARS-CoV-2 spike and different promising antibodies with the goal to identify the best candidate for sensor functionalization or virus inhibition. In this section, the interaction between the virus spike and the ACE2 enzyme, the target cell that SARS-CoV-2 use to infect human body, was also characterized. Finally, new antibodies were designed combining the previous ones with IgG1 and their behavior was studied in the presence of the sensor¿s silica surface and the nanoparticles gold surface used in the detector
  

DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS

• MAJORAL RAMONEDA, MARC: A Flexible System-on-Chip FPGA Architecture for Prototyping Experimental GNSS Receivers
  
  Author: MAJORAL RAMONEDA, MARC
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 03/04/2024
  Reading date: 10/05/2024
  Reading time: 11:00
  Reading place: Edifici C4-Aula 021B (Escola d'Enginyeria de Telecomunicació de Castelldefels)
  Thesis director: FERNANDEZ PRADES, CARLOS | ARRIBAS LÁZARO, JAVIER
  Committee:
       PRESIDENT: CAPARRA, GIANLUCA
       SECRETARI: BARTZOUDIS, NIKOLAOS
       VOCAL: FONT BACH, JOSEP ORIOL
  Thesis abstract: The rapid evolution in satellite navigation technology (GNSS) requires advanced prototyping tools for exploring new signals and developing innovative systems. Prototyping is essential in the design and development process, as it allows researchers to test and refine their ideas before implementing them on a large scale.Prototyping using commercial GNSS receivers poses several challenges. Currently, these receivers are primarily based on application-specific integrated circuits (ASICs), which are characterized by low power consumption, compact dimensions, and low cost, but offer limited flexibility. Although some commercial devices incorporate software-defined radio (SDR) techniques, they often contain proprietary code that restricts reconfiguration through an application programming interface (API) established by the manufacturer.GNSS receivers based on free and open-source software have become very valuable resources in the field of research and development, especially in satellite navigation. These receivers are highly valued for their adaptability and flexibility, allowing researchers to tailor the software to specific experimental needs or develop new signal processing algorithms. However, software-defined receivers tend to be less energy-efficient compared to hardware-based receivers, as they operate on general-purpose processors, which are not optimized for low power consumption.This thesis focuses on the design and development of a low-cost architecture for prototyping experimental GNSS receivers, based on System-on-Chip Field Programmable Gate Arrays (SoC FPGAs). This architecture overcomes the limitations of commercial GNSS receivers in terms of adaptability, flexibility, and reprogramming capacity, and offers improved energy efficiency compared to software-based receivers that rely on general-purpose processors. The strategy consists of combining the versatility of software-defined radio with the intensive parallelism and optimized energy consumption of programmable logic devices, providing the best of both worlds. This fusion allows the development of compact, portable GNSS receivers, thus facilitating the prototyping of embedded devices suitable for field testing. In addition, the GNSS processing core is based on a free and open-source software implementation, which provides detailed access to the signal processing chain and allows unrestricted exploration and modification of the algorithms used.This thesis also presents a design methodology for the development of new prototypes and new GNSS signal processing algorithms based on the proposed SoC FPGA architecture. This methodology places special emphasis on code reuse, a key aspect for reducing development costs and time.The practical applications of this architecture have been demonstrated through three prototypes: a GNSS receiver for low Earth orbit (LEO), a GNSS signal repeater, and a high-sensitivity GNSS receiver.The innovative approach presented in this thesis facilitates the development of experimental prototypes of flexible and portable GNSS receivers and signal generators, suitable for both laboratory experiments and field testing.
  
• UDAONDO GUERRERO, CARLOS: Analysis of Q factor degradation mechanisms in BAW resonators
  
  Author: UDAONDO GUERRERO, CARLOS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 22/03/2024
  Reading date: 17/06/2024
  Reading time: 11:00
  Reading place: Edifici C4-028-2, EETAC, Esteve Terradas, 7, Campus UPC, 08860.-Castelldefels (Barcelona)
  Thesis director: COLLADO GOMEZ, JUAN CARLOS | MATEU MATEU, JORDI
  Committee:
       PRESIDENT NO PRESENCIAL: AIGNER, ROBERT
       SECRETARI: VALENZUELA GONZALEZ, JOSE LUIS
       VOCAL NO PRESENCIAL: VILLANUEVA TORRIJO, LUIS GUILLERMO
  Thesis abstract: The emergence of smartphones not only changed the way people uses its phone for, but it also changed the traffic amount that networks need to carry, increasing the demand of higher data rates. The overall result was the appearance of 4G networks, and nowadays, the current development of 5G, implying the need for more frequency bands, and the application of new techniques such as Carrier Aggregation (CA), MIMO antennas, and so on. All these market driven necessities suppose a great challenge for the radiofrequency (RF) industry, which have been facing the necessity of miniaturization and band coexistence on its devices since the beginning of mobile communications.Microwave filters based on Bulk Acoustic Wave (BAW) resonators, have been able to this day to overcome these limitations. These devices consist in a thin piezoelectric layer comprised by two metal electrodes, and an acoustic confinement method, which can be simply made of air or a Bragg reflector. The use of electroacoustic technology enables to reduce the filter size up to five orders of magnitude, allowing the integration of multiple filters in handsets. This thesis focuses on modelling some of different physical phenomena at the resonator level that affect the performance of the filters.The first part of this thesis is the one regarding the spurious response of BAW resonators. This response is originated by acoustic waves traveling in the lateral dimension of the resonator. These waves couple electromechanically, degrading the filter response. BAW filters have been capable of overcoming this limitation suppressing them by the use of different electrode geometries (Apodization), or by surrounding the electrode by a decreased, or increased frame (Border Ring). The nature of these waves is studied through the thesis and several equivalent models are proposed in order to accurately predict them, helping to the design of the correspondent suppression structures. One of this thesis contributions regarding the lateral spurious resonances, consists in making use of a modified Mason model to determine the origin of the additional spurious resonances generated by the Border Ring. These resonances can be attributed to an acoustic mode, different from the fundamental, propagating across the resonator stack. By adding nonlinear sources to that model, the second harmonic (H2) emissions and the impact of the spurious resonances in them, is also studied.Finally, a new equivalent model based in the Transmission Line Matrix (TLM) method is proposed for the acoustic cavity of a BAW resonator. This new approach is able to model resonators with different electrode geometries, in a much faster way than traditionally used methods like the Finite Elements Method (FEM). In addition, by determining different propagation regions, it can be used to model both the apodization and the Border Ring at the same time.The second family of contributions are the ones regarding to the thermoelastic behavior of the BAW resonators. A solid heats up when compressed and vice versa. In a harmonic oscillation, when heat is able to flow through the solid regions, this flow from hotter to colder regions generates a relaxation of the acoustic wave. This is the thermoelastic damping. A thermo-electro-mechanical Mason model is used for quantifying this source of losses on BAW resonators. The model is compared with experimental data taken at cryogenic temperatures and an analysis of losses of the broadband spurious resonances of the Bragg reflector has been performed.
  

DOCTORAL DEGREE IN STRUCTURAL ANALYSIS

• AGUIRRE RUZ, ALEJANDRO: Numerical approximation of thin structures using stabilized mixed formulations for Infinitesimal and Finite Strain theories, including Fluid-Structure Interaction problem applications.
  
  Author: AGUIRRE RUZ, ALEJANDRO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN STRUCTURAL ANALYSIS
  Department: (DECA)
  Mode: Normal
  Deposit date: 22/04/2024
  Reading date: 24/05/2024
  Reading time: 12:00
  Reading place: Aula C1002, Edifici C1, Campus Nord ETSECCPB (Escola Tècnica Superior d'Engineria de Camins, Canals i Ports de Barcelona)
  Thesis director: CODINA ROVIRA, RAMON | BAIGES AZNAR, JOAN
  Committee:
       PRESIDENT: ROMERO OLLEROS, IGNACIO
       SECRETARI: ROSSI BERNECOLI, RICCARDO
       VOCAL NO PRESENCIAL: COLOMÉS GENÉ, JOSEP ORIOL
  Thesis abstract: The theories of thin structures can be classified into two main branches depending upon whether shear deformation in the transverse direction is taken into consideration or not. In this context, theories accounting for shear deformations prove suitable for modeling structures with both thin and thick profiles. In the Finite Element context, they are referred to as C0 theories due to the minimum continuity order of shape functions required to pose a discretized approximation. However, there are space incompatibilities in the standard discrete approximation that exhibits spurious solutions, particularly evident in thin structures. These instabilities, known as numerical locking, result in an artificial stiffening of the structure, whose effect becomes more pronounced for thinner structures. Various forms of numerical locking can be triggered, influenced not only by the slenderness of the structure but also by its shape and the nature of the applied loads. In this context, flat structures are prone to shear locking when exposed to transverse loads. Conversely, curved structures may confront different mechanisms leading to various forms of numerical locking, namely membrane, thickness, and trapezoidal locking. The initial part of the study aims to develop a specialized framework to address instabilities in the context of flat structures in the context of Reissner-Mindlin theory. Subsequently, the second part of the study aims to expand the framework to effectively address instabilities arising in of curved structures in the context of Solid-Shell elements. The locking problem is approached by means of a mixed formulation that considers displacements and stress as unknowns in a curvilinear coordinate framework. This approach allows to isolate the components of the stress tensor in order to study the mechanisms in which every type of numerical locking are triggered. The third part of the thesis is dedicated to integrating the previous advancements into Finite Strain analysis by the inclusion of standard hyperelastic constitutive behavior. With this approach, the problem becomes even more difficult to solve because of the non-linearity and the large deformations the shell is subject to. Lastly, the fourth and final part is dedicated to addressing the Fluid-Structure Interaction problem using an embedded mesh approach, which has consistently been a topic of great research interest in the literature, because of its complexity and wide variety of applications. This problem introduces a variety of challenges that have to be properly addressed: the discontinuous pressure field arising for the structure separating the fluid domain, the computation and imposition of transmission conditions between domains, the coupling strategy, and the algorithmic work needed to join all of these ingredients together. This thesis mainly focuses on overcoming challenges associated with thin structures when employing the conventional Galerkin Finite Element approach. It seeks solutions through stabilized methods, specifically within the Variational Multiscale framework. As result, the formulations developed through the investigations have proven to be robust, allowing to model locking-free thin structures efficiently, and to accurately describe the physics of thin shells immersed in fluid flows and being subject to large deformations.
  

DOCTORAL DEGREE IN SUSTAINABILITY

• CAICEDO MAFLA, MARÍA ANGÉLICA: Design of bike networks adaptive to heterogeneous demands and the needs of social groups. Case study: Bike mobility networks for the cities of Quito and Guayaquil, Ecuador.
  
  Author: CAICEDO MAFLA, MARÍA ANGÉLICA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SUSTAINABILITY
  Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
  Mode: Normal
  Deposit date: 11/04/2024
  Reading date: 13/06/2024
  Reading time: 11:00
  Reading place: ETSECCPB, C/Jordi Girona 1-3, edifici C1, sala 002, Campus Nord, Barcelona.
  Thesis director: ESTRADA ROMEU, MIGUEL ANGEL | MAYORGA CÁRDENAS, MIGUEL YURY
  Committee:
       PRESIDENT: DE OÑA, ROCÍO
       SECRETARI: MARTÍNEZ DÍAZ, MARGARITA
       VOCAL: MOURA BERODIA, JOSE LUIS
  Thesis abstract: Bike¿s recognition as a vital form of urban transportation underscores its capacity to enhance mobility, improve quality of life, and address several urban challenges such as air pollution, traffic congestion, and greenhouse gas emissions. This thesis explores bike¿s potential, emphasizing the importance of developing infrastructure, involving the community in mobility planning, and promoting policies to maximize its benefits.The study employs a dual-pronged approach to investigate the complexities of integrating cycling into urban transportation systems. It applies a sociological perspective to identify and assess barriers to bike use and their relationship with urban characteristics. Using ordered probit models, factors such as road insecurity, linked to the lack of adequate bike infrastructure, and topography, are highlighted. Concurrently, an engineering perspective guides the design of cycling networks to cater to varied demand, user types (differentiated by bike ownership and vehicle type), and topographies, reflecting real-world conditions. The optimal bike network results from minimizing the general system costs, including both agency and user costs. For flat terrains, continuous approximation techniques optimize network efficiency and accessibility, considering the heterogeneous demand and various user types, based on bike ownership and travel chains. In contrast, for cities with varied topographies, discrete approaches incorporate topographical elements into the model. Network performance and structure are evaluated based on two route selection criteria based on vehicle type: minimizing energy for traditional bike users and minimizing time for e-bike users. This engineering perspective aims to develop cycling networks that are practical and responsive to the diverse needs of urban dwellers.The methods are empirically validated through case studies in Quito and Guayaquil, Ecuador, showcasing their efficacy in developing adaptive bike networks tailored to diverse urban contexts, thereby significantly enhancing bike mobility across varied settings.The study's findings indicate that the network's layout, including lane spacing and station locations, is primarily influenced by the concentration of trip origins and destinations rather than topography. However, topography does affect route selection, which in turn influences flow distribution and infrastructure utilization. Moreover, the variation in trip distribution across different user types has a minimal impact on the network's lane configuration but significantly affects the number of bike-sharing stations and fleet size. The necessity for a safety stock at each station leads to an oversized fleet, increasing agency costs. Despite being an individual mode of transport, the study highlights that bike-sharing systems benefit from economies of scale. As demand increases and becomes more concentrated, the cost per user decreases, resulting in denser lane networks and improved network efficiency. E-bikes emerge as a viable solution for overcoming topographical barriers, offering a significant advantage in areas with steep slopes. For instance, where users of traditional bikes might need to walk, thereby increasing overall journey times, e-bike users experience reduced travel times and physical exertion, making e-bikes efficient in urban contexts with varied topographies.Future research directions and policy recommendations are proposed, highlighting the importance of a holistic and adaptive approach to bike mobility planning. This includes integrating diverse weather-related variables, exploring other personal mobility vehicles (PMVs), and employing robust datasets to inform sustainable urban transport strategies.
  
• ORNELAS HERRERA, SELENE IVETTE: PREFERENCIAS DE LOS CONSUMIDORES Y AGRICULTORES HACIA UN SISTEMA AGROALIMENTARIO MÁS SOSTENIBLE
  
  Author: ORNELAS HERRERA, SELENE IVETTE
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SUSTAINABILITY
  Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
  Mode: Normal
  Deposit date: 17/04/2024
  Reading date: 24/05/2024
  Reading time: 11:00
  Reading place: Sala Polivalente de la Escola d'Enginyeria Agroalimentària i de Biosistemes de Barcelona (Castelldefels)
  Thesis director: KALLAS CALOT, ZEIN
  Committee:
       PRESIDENT: SÁNCHEZ GARCÍA, M. MERCEDES
       SECRETARI: RAHMANI MEDDOUR, DJAMEL
       VOCAL: IGLESIAS MARTÍNEZ, EVA
  Thesis abstract: The adaptation of the agri-food system towards more sustainable models is a pressing need to guarantee food security for current and future generations, in the face of population growth, scarce natural resources and climate change. To meet the challenges of producing more sustainably, new food production systems have been developed, they incorporate the principles of circular economy. Circular production systems reduce the consumption of new external inputs and the generation of waste, reducing adverse environmental effects and allowing the recovery of nutrients. This thesis addresses two of the main links in the shortest value chain of the agri-food system, "the producer and the consumer", and their response towards the incorporation of sustainability approaches, such as circularity. The objective is to analyze whether the circular agriculture practices identified as more sustainable are accepted by agricultural producers and the factors that influence their adoption, as well as the preference of consumers and their willingness to pay for these circular production innovations, in order to try to convert the results obtained into evidence that can serve as a basis for generating adequate and coherent public policies, to support and facilitate the adoption of circular innovations. . In relation to the above, in the first instance a semi-structured questionnaire was applied to agricultural producers from: Spain, Austria, Czech Republic and Italy, in which the hierarchical analysis method (AHP) to measure preferences and the scale of the New Ecological Paradigm NEP were included to measure environmental attitudes. Results showed an adoption readiness of 48.24% and that the acceptance of the proposed circular innovations is closely related to the environmental objectives, level of education, previous adoption experience and environmental attitudes of farmers. We also found that institutional support plays an important role in adoption decisions. With regard to consumers, in a first approach, through a survey of 5,246 consumers in Germany, the Netherlands, Italy, the Czech Republic and Spain, their willingness to pay for beef fillet produced in a circular livestock system was analyzed, using the Discrete Choice Experiments (DCE) method. This study included the analysis of the behaviors that influence their preferences, based on the Theory of Planned Behavior (TPB). The results allowed us to observe that there is a potential market for circular beef fillet. Although preferences are heterogeneous, consumers are generally willing to pay a higher premium for circular beef steak than conventional steak and lower than for organic beef. Of the components of planned behavior theory, social norms and behavioral control perception increased preferences for circular production beef steak, while environmental attitudes increased preferences for organic beef steak, and reduced preference for conventional beef steak. Subsequently, the preferences of 5,591 consumers in Spain, Poland, Italy, Hungary, Croatia and Belgium were analyzed, as well as their willingness to pay for pork, milk and bread labelled as circular and presented as more sustainable, in terms of reducing greenhouse gas emissions and optimizing nutrients. This analysis included sustainable consumption behavior, focused on purchasing, use, and recycling habits. The results showed that about 27% of participating consumers preferred foods from circular systems. As in the previous study, the results highlighted the importance of consumers' environmental attitudes in determining their preferences for environmentally sustainable products. All of the above results on consumers allow us to suggest to governments, policy makers and other sectors involved in sustainable food production, the standardization of food labels obtained through circular agriculture systems and the design of educational programs to increase knowledge about the problems generated by unsustainable consumption habits.
  
• PAZMIÑO FLORES, YADIRA CARMEN: Evaluación de los usos de suelo y valor ecosistémico del páramo de la Subcuenca Chambo (Ecuador)
  
  Author: PAZMIÑO FLORES, YADIRA CARMEN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SUSTAINABILITY
  Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
  Mode: Article-based thesis
  Deposit date: 17/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: FELIPE BLANCH, JOSE JUAN DE | VALLBE MUMBRU, MARC
  Committee:
       PRESIDENT: AGUILERA BENAVENTE, FRANCISCO
       SECRETARI: ALCARAZ SENDRA, OLGA
       VOCAL: GUAITA PRADAS, INMACULADA
       VOCAL NO PRESENCIAL: HERNÁNDEZ CLEMENTE, ROCÍO
       VOCAL NO PRESENCIAL: GILABERT NAVARRO, M. DESAMPARADOS
  Thesis abstract: The scarcity of information that allows understanding the importance of natural resources from an economic approach is a limitation to establish parameters related to environmental investment in conservation plans. This research proposes a methodology that allows modeling the variability of páramo land uses and the Ecosystem Valuation (EV) of the Chambo-Ecuador sub-basin from a bioeconomic monitoring that links the economic rent of páramo land uses with remote sensing tools and geographic information systems. The main results of the methodology determined that temporal monitoring of land covers is essential to identify areas of greatest vulnerability to EV degradation. The thresholds, functions and interrelationships determined in the Cart Decision Tree (CDT), Multilayer Perception (MLP), Multivariate Adaptive Regression Splines (MARS) and Support Vector Machines (SVM) models for land cover recognition were efficient; the models performed 88%, 85%, 83% and 81% respectively. The hybridization of the models, Markov chains and cellular automata was appropriate for predicting future land cover changes in Andean areas in relation to their VE, the methods achieved acceptable accuracy for recognizing páramo land uses. The variables chosen for land cover classification were adequate to identify land cover particularities.The opportunity cost and benefit transfer methods proposed obtained a good performance in the evaluation of food production trajectories linked to environmental services (ES) of carbon supply and concentration associated with indirect and support ES, so it was determined that the information from the dynamics of environmental services is an important indicator to understand the real state of the resource and consequently allows understanding the necessary strategies to undertake sustainable actions for ecological management.The mapping generated allowed us to determine that the páramo decreased by 13% between 2000-2010 and 19% between 2010-2020. It was estimated that the loss of the ecosystem between 2000 and 2030 will increase to 28%. From the first year of the study to the last year considered in the work, the páramo will go from occupying 92% to 64% of the area studied. The changes in the EV reveal that the categories with anthropogenic activity analyzed maintain a constant growth that has a direct impact on the EV of the páramo. The most affected areas are those up to 3500 meters above sea level. The EV of the Chambo sub-basin from 2000 to 2020 will increase from 2.86×108 USD to 2.59×108 USD and it is estimated that by 2030 the EV will decrease to 2.48×108 USD, which leads us to recognize that, although the loss of the EV of the natural resource is not critical, its degradation is increasing.Through this methodology it will be possible to obtain, in a practical way, data on the conservation status of the resource over time, allowing to solve problems related to the scarcity of data and leading to the understanding of changes in the area from a socioecological approach, i.e., covering the environmental impacts of human activities on natural systems. The basis of the developed method allows replication of the methodology.The information generated by this study will be of vital importance to understand the causes of the changes in the Andean systems in monetary and environmental terms, which will allow the development of management plans and conservation policies aimed at protection and sustainable management from an economic approach.
  
• RAMIREZ GARRIDO, ROSEMBER: Evaluación del Riesgo Ambiental de las Nanopartículas de Plata (AgNPs) en Ecosistemas Acuáticos
  
  Author: RAMIREZ GARRIDO, ROSEMBER
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SUSTAINABILITY
  Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
  Mode: Normal
  Deposit date: 18/04/2024
  Reading date: 10/06/2024
  Reading time: 11:00
  Reading place: ETSEIB (Sala de audiovisuales del pavellón G, 2 planta, Campus Sud, Barcelona). Avda. Diagonal, 647
  Thesis director: DARBRA ROMAN, ROSA MARIA | MARTI GREGORIO, VICENÇ
  Committee:
       PRESIDENT: DE PABLO RIBAS, JOAN
       SECRETARI: SANCHÍS SANDOVAL, JOSEP ÀNGEL
       VOCAL: DÍAZ CRUZ, SILVIA
  Thesis abstract: The widespread and increasing use of silver nanoparticles (AgNPs) in various products is leading to their release into different environmental compartments, especially into aquatic environments. These particles can enter these environments through various pathways, for example, gradually via effluents from wastewater treatment plants (WWTPs) or accidentally through spills onto soil or into rivers. This thesis presents a detailed analysis of the transport (advection-dispersion) and dispersion of silver nanoparticles (AgNPs) in both surface and groundwater, considering mass balances, various mathematical models, and factors influencing their mobility and retardation. For surface waters, continuous and point discharges are considered, and an analytical model is used to represent the behavior of AgNPs in the river. For groundwater, point discharges are considered. The interaction of AgNPs with porous media in groundwater (retardation process) is also taken into account, which allows for the calculation of the maximum concentration of AgNPs in groundwater. Initially, a Fuzzy Logic model is developed to assess the environmental risk in aquatic ecosystems based on the concentration and toxicity of AgNPs. The toxicity is determined with great adaptability by including variables such as shape, size, and coating of the nanoparticles, allowing a more accurate risk assessment. This model is applied to a discharge of AgNPs into the river from WWTP effluents or an accident. The results show that in all cases, the risk of AgNPs due to direct accidental discharge into the river poses a higher risk than that from WWTPs. Subsequently, a hybrid model is developed that integrates Monte Carlo simulation (for concentration calculation) with the developed Fuzzy Logic model. This integration provides a tool for assessing the environmental risk of AgNPs due to a spill onto the soil. Two scenarios are proposed after the spill: discharge of AgNP-contaminated aquifer water into the river and use of this aquifer water for wetland recharge. The concentration distribution of AgNPs by river discharge is below the proposed legal limit, while in the wetland use scenario, legal limits are not met in any case, indicating a higher risk associated with this latter use. After conducting a sensitivity analysis, it has been proved that the developed Hybrid model, which combines Fuzzy Logic and Monte Carlo techniques, is a useful and versatile tool for managing uncertainty in risk assessment.